A low-sensitization non-irritating child outdoor protection essential oil and a preparation method thereof

Abstract

The present application belongs to the technical field of children's skin care, and discloses a low-sensitivity and non-irritating children's outdoor protection essential oil and a preparation method thereof. The essential oil comprises a biomimetic sebum film base oil and a solid-liquid dual sustained-release system dispersed in the biomimetic sebum film base oil. The biomimetic sebum film base oil comprises refined squalane, cold-pressed camellia seed oil, jojoba oil and ceramide NP, and can maintain a weakly acidic environment on the skin surface after being applied on the skin surface. The solid-liquid dual sustained-release system uses glyceryl behenate and cetyl palmitate as composite wall materials, and encapsulates de-furan coumarin citronella essential oil and real lavender essential oil to obtain solid lipid nanoparticles with a particle size of 150 nm to 250 nm. The product has the advantages of long-acting protection and low irritation, can realize smooth and slow release of active ingredients to prolong the protection time, has a far lower sensitization activation index than the safety threshold, is suitable for the fragile skin of children, can maintain a weakly acidic steady state of the skin, improve the skin barrier water-locking capacity, and has a better protection effect than traditional mineral oil-based and non-encapsulated essential oil products.

Description

Technical Field

[0001] This invention belongs to the field of children's skin care technology, and in particular to a low-allergenic, non-irritating outdoor protective essential oil for children and its preparation method. Background Technology

[0002] The children's outdoor skincare sector is a high-growth sub-sector within the daily chemical industry. Its core application is skin protection for children during outdoor activities and play, aiming to simultaneously resist external irritants, reduce the risk of allergies, and maintain the homeostasis of children's skin barrier. In recent years, as parents have become increasingly concerned about children's skin health, children's outdoor skincare products that combine low irritation and long-lasting protection have become a core R&D need in the industry.

[0003] Currently, mainstream outdoor protective products for children fall into two categories. The first category is mineral oil-based protective oil, which works by forming a dense physical barrier film on the skin's surface using mineral oil to block irritants such as insect bites and external dust from contacting the skin. This type of product has low production costs and a fast film-forming speed, and currently accounts for more than 60% of the application in low- to mid-range children's protective products. However, it has poor compatibility with children's natural sebum, and long-term use can disrupt the slightly acidic environment of the skin's surface, increase transepidermal water loss, and easily cause dry skin and redness. In addition, some mineral oils with insufficient purification may contain residual impurities that pose a higher risk of allergies.

[0004] The second category is plant-based essential oil protective products. These rely on the active ingredients of natural plant extracts such as citronella oil and lavender oil to achieve insect-repelling and soothing effects. Their natural ingredients and superior skin affinity compared to mineral oil-based products have led to their increasing use in mid-to-high-end children's skincare product lines in recent years. However, these products do not effectively encapsulate the active essential oils, resulting in rapid evaporation of the active ingredients. A single application provides protection for less than two hours. Furthermore, citronella oil that has not undergone furanocoumarin removal treatment has strong photosensitivity, which can easily cause photosensitive dermatitis in children when used outdoors. The large-scale release of active ingredients in a short period without controlled-release treatment further increases the probability of skin sensitization.

[0005] The two existing mainstream technologies cannot simultaneously meet the multiple requirements of children's outdoor protective products for low allergenicity, long-lasting protection, and maintenance of skin barrier homeostasis. They have prominent defects such as skin barrier damage, high risk of allergy, and short protection time. The industry urgently needs new protective products that are adapted to the physiological characteristics of children's skin to fill the technological gap. Summary of the Invention

[0006] In view of the shortcomings of existing outdoor protective products for children, such as easy damage to the skin barrier, high risk of allergies, and short duration of protection, this invention provides a hypoallergenic and non-irritating outdoor protective essential oil for children and its preparation method.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: A hypoallergenic and non-irritating outdoor protective essential oil for children comprises a biomimetic sebum film base oil and a solid-liquid dual sustained-release system dispersed in the biomimetic sebum film base oil; the biomimetic sebum film base oil contains refined squalane, cold-pressed camellia seed oil, jojoba oil and ceramide NP, which helps maintain the slightly acidic environment of the skin surface after being applied; the solid-liquid dual sustained-release system uses behenic acid glyceride and cetyl palmitate as composite wall materials to encapsulate defuranocoumarin lemongrass essential oil and real lavender essential oil to obtain solid lipid nanoparticles with a particle size of 150nm~250nm.

[0008] Furthermore, the mass of the ceramide NP accounts for 0.5% to 1.5% of the total mass of the biomimetic sebum film base oil.

[0009] Furthermore, the designed molar ratio of refined squalane, cold-pressed camellia seed oil, and jojoba oil is 1~2:3~4:2~3, and the mass ratio range calculated based on the average molecular weight of each raw material is 1.2~2.4:2.3~3.2:2.1~3.3; wherein refined squalane is a pure hydrocarbon compound with a molecular weight of 422, cold-pressed camellia seed oil is calculated based on the average molecular weight of its main component, oleic acid triglyceride, and jojoba oil is calculated based on the average molecular weight of its main long-chain wax ester component. A preferred mass ratio is 1.8~2.2:2.5~3.0:2.4~2.8.

[0010] Furthermore, the mass ratio of behenicol glyceryl ester to cetyl palmitate is 2~3:1.

[0011] Furthermore, the mass ratio of the defuranocoumarin citronella essential oil to the real lavender essential oil is 1.5~2.5:1, and the total mass of the defuranocoumarin citronella essential oil and the real lavender essential oil accounts for 15%~25% of the total mass of the solid-liquid dual sustained-release system.

[0012] Furthermore, the mass of the solid-liquid dual sustained-release system accounts for 8% to 15% of the total mass of the protective essential oil.

[0013] Furthermore, the sensitization activation index (SI) of the protective essential oil is characterized by being significantly lower than the positive threshold of 2.0 in the OECD 442E standard, preferably SI < 1.5; the cumulative release rate of the active ingredient of the protective essential oil after 24 hours in an in vitro Franz diffusion cell test is less than 60%, the transdermal water loss rate of the skin after application is reduced by more than 30% compared with the use of mineral oil-based protective oil, and the change rate of extracellular calcium and potassium ion concentration is less than 5%.

[0014] Further steps include the following: S1. Weigh out refined squalane, cold-pressed camellia seed oil, jojoba oil and ceramide NP according to the formula, mix them evenly to obtain biomimetic sebum film base oil, sterilize and set aside. S2. Weigh behenic acid glycerides and cetyl palmitate according to the ratio, heat to a molten state, add soybean lecithin accounting for 2%~5% of the total mass of the oil phase wall material, mix evenly to obtain an oil phase wall material containing emulsifier, add defuranocoumarin lemongrass essential oil and real lavender essential oil to the oil phase wall material, stir evenly to obtain a mixed oil phase. S3. Add the mixed oil phase to the phosphate buffer solution preheated to the same temperature, and disperse it by high-speed shearing to obtain the primary emulsion. Then, perform high-pressure homogenization on the primary emulsion to obtain a solid lipid nanoparticle dispersion, and freeze-dry it to obtain solid lipid nanoparticle powder. S4. Add solid lipid nanoparticle powder to biomimetic sebum film base oil and stir to disperse evenly; S5. The evenly dispersed protective essential oil is filtered through a 0.22μm hydrophobic polytetrafluoroethylene microporous membrane for sterilization to obtain the finished product.

[0015] Furthermore, in S2, the heating temperature is 75℃~85℃; in S3, the preheating temperature of the phosphate buffer solution and the temperature difference between the mixed oil phase do not exceed 2℃; the high-speed shearing speed is 8000rpm~12000rpm; and the shearing time is 3min~5min. In S5, the hydrophobic microporous filter membrane is made of polytetrafluoroethylene.

[0016] Furthermore, in S3, the pressure of high-pressure homogenization is 800 bar to 1200 bar, the number of homogenization cycles is 3 to 5, the cold trap temperature for freeze drying is -45°C to -55°C, and the drying time is 24 h to 36 h; in S4, the stirring and dispersion speed is 300 rpm to 500 rpm, the dispersion time is 10 min to 15 min, and the system temperature during the dispersion process is controlled at 20°C to 30°C.

[0017] The present invention has the following beneficial effects: This invention uses a biomimetic sebum film base oil that is highly compatible with the natural sebum components of children. It uses refined squalane, cold-pressed camellia seed oil, jojoba oil, and ceramide NP as the oil phase base. After application, it can adapt to the physiological environment of the skin surface, maintain a slightly acidic homeostasis, reduce the loss of the skin's own moisture, and leave no additional irritating impurities. It effectively solves the defects of existing mineral oil-based protective products, such as poor compatibility with sebum, easy damage to the skin barrier, and causing dryness and redness.

[0018] This invention employs a solid-liquid dual sustained-release system to carry active protective components. It uses a compound of behenicol glyceryl ester and cetyl palmitate as a composite wall material to prepare solid lipid nanoparticles of a specific particle size, which stably encapsulate the active essential oils. This enables the smooth and continuous release of active substances, prolonging the effective protection time after a single application. It effectively solves the defects of existing unencapsulated plant essential oil products, such as rapid evaporation of active substances and short protection time.

[0019] This invention uses defuranocoumarin-derived lemongrass essential oil combined with real lavender essential oil as active protective ingredients. The controlled release effect of nanoparticles prevents the active ingredients from coming into contact with the skin in large quantities in a short period. The product's sensitization activation index is far below the internationally accepted skin sensitization positive threshold, while also eliminating the photosensitivity risk of lemongrass essential oil. This effectively solves the shortcomings of existing protective products, such as high sensitization risk and the tendency to cause photosensitive dermatitis when used outdoors. This product is suitable for the skin physiology of children of all ages and can be used in various outdoor scenarios such as field trips, school outdoor sports, and daily outings. It achieves both skin barrier maintenance and protection against outdoor irritation without the need for additional skincare products, making it highly valuable for promotion and application in the field of children's daily skincare. Attached Figure Description

[0020] Figure 1 This is a flowchart of a method for preparing a low-sensitivity, non-irritating outdoor protective essential oil for children, as proposed in this invention. Figure 2 This is a line graph showing the cumulative release of active ingredients over 24 hours as proposed in this invention. Figure 3 The bar chart shows the TEWL reduction rate of different formulations proposed in this invention. Figure 4 This is a bar chart of the SI (sensitization activation index) for the h-CLAT method proposed in this invention. Detailed Implementation

[0021] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] The reagents used in this experiment were as follows: refined squalane was food grade, with a purity ≥99%; cold-pressed camellia seed oil was first-grade cold-pressed, with an acid value ≤0.2mgKOH / g; jojoba oil was first-grade cold-pressed, with an iodine value of 80-85gI2 / 100g; ceramide NP purity ≥98%; behenyl glycerol purity ≥99%; cetyl palmitate purity ≥99%; furanocoumarin content in citronellol essential oil was <0.1ppm; linalool content in real lavender essential oil was 32%; soybean lecithin was injection grade, with a purity ≥98%; phosphate buffer pH 7.4 was prepared using standard laboratory methods. 2,4-dinitrochlorobenzene (DNCB) was analytical grade, with a purity ≥98%.

[0023] Example 1 The hypoallergenic and non-irritating outdoor protective essential oil formula for children in this embodiment is as follows: the total mass of the biomimetic sebum film base oil accounts for 92% of the total mass of the protective essential oil, of which the mass ratio of refined squalane, cold-pressed camellia seed oil, and jojoba oil is 1.2:2.3:2.1, and the mass of ceramide NP accounts for 0.5% of the total mass of the biomimetic sebum film base oil; the total mass of the solid-liquid dual sustained-release system accounts for 8% of the total mass of the protective essential oil, of which the mass ratio of behenic acid glyceride to cetyl palmitate is 2:1, the mass ratio of defuranocoumarin citronella essential oil to real lavender essential oil is 1.5:1, and the total mass of defuranocoumarin citronella essential oil and real lavender essential oil accounts for 15% of the total mass of the solid-liquid dual sustained-release system.

[0024] The preparation steps in this embodiment are as follows: S1. Weigh out refined squalane, cold-pressed camellia seed oil, jojoba oil and ceramide NP according to the ratio, place them in a sterilized conical flask, stir at 300 rpm for 10 min to mix evenly to obtain biomimetic sebum film base oil, sterilize at 121℃ high pressure steam for 15 min and cool to room temperature for later use. S2. Weigh out behenicol glyceryl ester and cetyl palmitate according to the ratio, heat to 75°C until completely melted, add soybean lecithin accounting for 2% of the total mass of the oil phase wall material, stir at 200 rpm for 5 minutes to mix evenly to obtain an oil phase wall material containing emulsifier, add defuranocoumarin lemongrass essential oil and real lavender essential oil to the oil phase wall material, stir at 300 rpm for 3 minutes to mix evenly to obtain a mixed oil phase; S3. The mixed oil phase was added to phosphate buffer preheated to 74°C and dispersed by high-speed shearing to obtain a primary emulsion. The high-speed shearing speed was 8000 rpm and the shearing time was 3 min. The primary emulsion was subjected to high-pressure homogenization to obtain a solid lipid nanoparticle dispersion. The high-pressure homogenization pressure was 800 bar and the homogenization cycle was 3 times. The dispersion was transferred to a freeze dryer with the cold trap temperature set to -45°C and the drying time was 24 h. After freeze-drying, solid lipid nanoparticle powder was obtained. The solid lipid nanoparticles prepared in this example had an average particle size of 152 nm, a polydispersity index (PDI) of 0.12, and were uniformly distributed without agglomeration. S4. Add solid lipid nanoparticle powder to biomimetic sebum film base oil, stir and disperse evenly. The stirring speed is 300 rpm, the dispersion time is 10 min, and the system temperature is controlled at 20℃ during the dispersion process. S5. The evenly dispersed protective essential oil is filtered through a 0.22μm hydrophobic polytetrafluoroethylene microporous membrane for sterilization to obtain the finished product.

[0025] Example 2 The hypoallergenic and non-irritating outdoor protective essential oil formula for children in this embodiment is as follows: the total mass of the biomimetic sebum film base oil accounts for 88% of the total mass of the protective essential oil, of which the mass ratio of refined squalane, cold-pressed camellia seed oil, and jojoba oil is 1.8:2.7:2.5, and the mass of ceramide NP accounts for 1.0% of the total mass of the biomimetic sebum film base oil; the total mass of the solid-liquid dual sustained-release system accounts for 12% of the total mass of the protective essential oil, of which the mass ratio of behenic acid glyceride to cetyl palmitate is 2.5:1, the mass ratio of defuranocoumarin citronella essential oil to real lavender essential oil is 2:1, and the total mass of defuranocoumarin citronella essential oil and real lavender essential oil accounts for 20% of the total mass of the solid-liquid dual sustained-release system.

[0026] The preparation steps in this embodiment are as follows: S1. Weigh out refined squalane, cold-pressed camellia seed oil, jojoba oil and ceramide NP according to the ratio, place them in a sterilized conical flask, stir at 300 rpm for 10 min to mix evenly to obtain biomimetic sebum film base oil, sterilize at 121℃ high pressure steam for 15 min and cool to room temperature for later use. S2. Weigh behenic acid glyceride and cetyl palmitate according to the formula, heat to 80°C until completely melted, add soybean lecithin accounting for 3.5% of the total mass of the oil phase wall material, stir at 200 rpm for 5 minutes to mix evenly to obtain an oil phase wall material containing emulsifier, add defuranocoumarin lemongrass essential oil and real lavender essential oil to the oil phase wall material, stir at 300 rpm for 3 minutes to mix evenly to obtain a mixed oil phase; S3. The mixed oil phase was added to phosphate buffer preheated to 79°C and dispersed by high-speed shearing to obtain a primary emulsion. The high-speed shearing speed was 10000 rpm and the shearing time was 4 min. The primary emulsion was subjected to high-pressure homogenization to obtain a solid lipid nanoparticle dispersion. The high-pressure homogenization pressure was 1000 bar and the homogenization cycle was 4 times. The dispersion was transferred to a freeze dryer with the cold trap temperature set to -50°C and the drying time was 30 h. After freeze-drying, solid lipid nanoparticle powder was obtained. The solid lipid nanoparticles prepared in this example had an average particle size of 201 nm, a polydispersity index (PDI) of 0.11, and were uniformly distributed without agglomeration. S4. Add solid lipid nanoparticle powder to biomimetic sebum film base oil, stir and disperse evenly. The stirring speed is 400 rpm, the dispersion time is 12 min, and the system temperature is controlled at 25℃ during the dispersion process. S5. The evenly dispersed protective essential oil is filtered through a 0.22μm hydrophobic polytetrafluoroethylene microporous membrane for sterilization to obtain the finished product.

[0027] Example 3 The hypoallergenic and non-irritating outdoor protective essential oil formula for children in this embodiment is as follows: the total mass of the biomimetic sebum film base oil accounts for 85% of the total mass of the protective essential oil, of which the mass ratio of refined squalane, cold-pressed camellia seed oil, and jojoba oil is 2.4:3.2:3.3, and the mass of ceramide NP accounts for 1.5% of the total mass of the biomimetic sebum film base oil; the total mass of the solid-liquid dual sustained-release system accounts for 15% of the total mass of the protective essential oil, of which the mass ratio of behenic acid glyceride to cetyl palmitate is 3:1, the mass ratio of defuranocoumarin citronella essential oil to real lavender essential oil is 2.5:1, and the total mass of defuranocoumarin citronella essential oil and real lavender essential oil accounts for 25% of the total mass of the solid-liquid dual sustained-release system.

[0028] The preparation steps in this embodiment are as follows: S1. Weigh out refined squalane, cold-pressed camellia seed oil, jojoba oil and ceramide NP according to the ratio, place them in a sterilized conical flask, stir at 300 rpm for 10 min to mix evenly to obtain biomimetic sebum film base oil, sterilize at 121℃ high pressure steam for 15 min and cool to room temperature for later use. S2. Weigh out behenicol glyceryl ester and cetyl palmitate according to the formula, heat to 85°C until completely melted, add soybean lecithin accounting for 5% of the total mass of the oil phase wall material, stir at 200 rpm for 5 minutes to mix evenly to obtain an oil phase wall material containing emulsifier, add defuranocoumarin lemongrass essential oil and real lavender essential oil to the oil phase wall material, stir at 300 rpm for 3 minutes to mix evenly to obtain a mixed oil phase; S3. The mixed oil phase was added to phosphate buffer preheated to 84°C and dispersed by high-speed shearing to obtain a primary emulsion. The high-speed shearing speed was 12000 rpm and the shearing time was 5 min. The primary emulsion was subjected to high-pressure homogenization to obtain a solid lipid nanoparticle dispersion. The high-pressure homogenization pressure was 1200 bar and the homogenization cycle was 5 times. The dispersion was transferred to a freeze dryer with the cold trap temperature set to -55°C and the drying time was 36 h. After freeze-drying, solid lipid nanoparticle powder was obtained. The solid lipid nanoparticles prepared in this example had an average particle size of 247 nm, a polydispersity index (PDI) of 0.13, and were uniformly distributed without agglomeration. S4. Add solid lipid nanoparticle powder to biomimetic sebum film base oil, stir and disperse evenly. The stirring speed is 500 rpm, the dispersion time is 15 min, and the system temperature is controlled at 30℃ during the dispersion process. S5. The evenly dispersed protective essential oil is filtered through a 0.22μm hydrophobic polytetrafluoroethylene microporous membrane for sterilization to obtain the finished product.

[0029] Comparative Example 1 This comparative example is a control sample without ceramide NP. Except for the fact that ceramide NP is not added to the biomimetic sebum film base oil, the other formulation components, ratios, and preparation parameters are completely consistent with those of Example 2. The solid lipid nanoparticles prepared in this comparative example have an average particle size of 203 nm, a polydispersity index (PDI) of 0.12, and are uniformly distributed without agglomeration.

[0030] Comparative Example 2 This comparative example is a control sample of traditional non-encapsulated essential oils. Except for not preparing solid lipid nanoparticles, and directly adding defuranocoumarin lemongrass essential oil and real lavender essential oil to the biomimetic sebum film base oil according to the ratio of Example 2 and stirring and dispersing, the other formulation components, ratios, and preparation parameters are completely consistent with Example 2. The biomimetic sebum film base oil used is the same as that in Example 2, containing 1.0% ceramide NP.

[0031] Core performance testing methods Encapsulation efficiency was determined by high performance liquid chromatography (HPLC). The chromatographic conditions were as follows: C18 column (4.6 mm × 250 mm, 5 μm), mobile phase: methanol:water = 80:20 (v / v), flow rate: 1 mL / min, detection wavelength: 210 nm, column temperature: 30 ℃, and injection volume: 20 μL.

[0032] Standard curve construction: Citronellol standard with a purity ≥98% and linalyl acetate standard with a purity ≥99% were diluted with methanol to prepare mixed standard solutions of various concentrations. After injection and detection, a standard curve was plotted based on peak area versus concentration. The linear range of citronellol is 0.2 μg / mL to 25 μg / mL. The standard curve is Y = 12563X + 213.4 (where Y is the peak area and X is the citronellol concentration in μg / mL), with a correlation coefficient R. 2 =0.9998; the linear range of linalyl acetate is 0.5 μg / mL to 30 μg / mL, and the standard curve is Y = 9872X + 187.6 (Y is the peak area, X is the concentration of linalyl acetate in μg / mL), with a correlation coefficient R. 2 =0.9997. The blank excipient did not interfere with the target peak position, indicating good method specificity; the recoveries of both active ingredients were between 97.5% and 102.5%, and the method accuracy met the requirements.

[0033] Sample determination: Total active ingredient content: Take an appropriate amount of solid lipid nanoparticle powder, add methanol and sonicate for 10 min, make up to volume, filter through a 0.22 μm organic filter membrane, inject and determine, and calculate the total mass W of the added active ingredients. 总 ; Free active ingredient content: Take an appropriate amount of solid lipid nanoparticle powder, reconstitute it with phosphate buffer (pH 7.4) to form a dispersion, centrifuge at high speed (15000 rpm, 4℃, 20 min), filter the supernatant through a 0.22 μm filter membrane, and inject it for analysis. Calculate the mass W of free active ingredient. 游离 The encapsulation ratio is calculated as follows: Encapsulation ratio = (W...) 总 -W 游离 ) / W 总 ×100%, where W 总 W represents the total mass of active ingredients added. 游离 This represents the mass of the free active ingredient.

[0034] Franz release assay: A modified Franz diffusion cell with a receiving chamber volume of 7 mL was used. The receiving solution was a pH 7.4 phosphate buffer solution containing 20% ​​ethanol. The stirring speed was 300 rpm, and the system temperature was controlled at 32℃. The diffusion membrane was a PVDF membrane with a pore size of 0.22 μm. 100 μL of sample was uniformly coated on the membrane surface. 1 mL of receiving solution was collected at 0.5, 1, 2, 4, 8, 12, and 24 h, and an equal volume of isothermal blank receiving solution was added. The collected receiving solution was filtered through a 0.22 μm organic filter membrane, and the content of active ingredients was detected by HPLC. The cumulative release rate was calculated.

[0035] Sensitization activation index (SI) determination: The h-CLAT method according to OECD 442E standard was used. THP-1 cells were incubated for 24 hours and the expression rates of CD86 and CD54 were detected. The SI value was calculated and SI ≥ 2.0 was considered as sensitization positive.

[0036] Skin pH test: Using the EpiSkin 3D recombinant human epidermal model, 20 μL of sample was evenly spread on the model surface. The pH value of the model surface was measured at 0, 1, 2 and 4 h using a skin surface pH meter. Before the test, the residual sample on the model surface was gently rinsed off with pH 7.4 phosphate buffer, and the surface liquid was blotted dry before the test.

[0037] Transdermal water loss (TEWL) test: The EpiSkin 3D reconstructed human epidermal model was used for testing. The skin moisture loss tester was used and the test was conducted in accordance with the GB / T 38165-2019 standard. Commercially available children's mineral oil-based protective oil of the same type was used as a positive control. The TEWL reduction rate was calculated.

[0038] Extracellular ion concentration assay: EpiSkin 3D recombinant human epidermal model was used. After 24 hours of sample application, the culture supernatant below the model was collected. Calcium and potassium ion concentrations were detected by ion chromatography and the change rate was calculated by comparing with the blank control group without sample application.

[0039] Test data table and explanation Table 1 Summary of core performance parameters for each test group

[0040] This table summarizes the core performance test results of each test group. The nanoparticle size of the three examples is in the range of 150~250nm, the encapsulation rate of the two active ingredients is ≥70%, and the cumulative release rate after 24h is less than 60%, which shows excellent sustained-release performance and can effectively extend the protection time and solve the defect of short protection time of existing products.

[0041] The SI values ​​of all three examples were below 1.5, far below the OECD-specified positive threshold of 2.0. Skin pH remained stable within the natural weakly acidic range of 5.5-6.0, and the calcium and potassium ion change rates were all below 5%. The TEWL reduction rate exceeded 30%, effectively maintaining skin barrier integrity, reducing the risk of sensitization, and addressing the shortcomings of existing products that damage the skin barrier and pose a high risk of sensitization. Comparative Example 1 showed a decreased TEWL reduction effect after the absence of ceramide NP, confirming the role of ceramide NP in barrier maintenance. Comparative Example 2, without nano-encapsulation, showed no sustained-release effect, increased sensitization risk, and disruption of barrier homeostasis, confirming the core role of the sustained-release system.

[0042] Table 2. Results of h-CLAT Sensitization Test

[0043] This table presents the sensitization test results using the h-CLAT method. The average SI value of the three batches of Sample 2 from Example 2 was 1.3 ± 0.1, which is close to the detection value of the negative control, pure squalane, and lower than the positive threshold of 2.0 specified in the OECD 442E standard. It is also significantly lower than the detection value of Comparative Example 2, demonstrating that the combination of defuranocoumarin essential oil and nano-controlled release technology used in this invention can effectively reduce the sensitization of the product, addressing the high sensitization risk of existing plant essential oil products. The detection value of the positive control, DNCB, is much higher than the positive threshold, proving that the testing system is stable and effective, and the test results are reliable.

[0044] refer to Figure 2 This figure visually illustrates the release patterns of the active ingredients in the two formulations. The cumulative release rate of Example 2 over 24 hours was only 55.3%, far lower than the 92.4% of Comparative Example 2. Furthermore, the release process was stable without any sudden release, verifying the controlled-release effect of the solid-liquid dual sustained-release system. This sustained-release characteristic avoids irritation caused by a large amount of active ingredient contacting the skin in a short period, and prolongs the duration of action of the active ingredient, maintaining a stable outdoor protective effect without frequent reapplication. This effectively addresses the core shortcomings of existing non-encapsulated essential oil products, such as short protective duration and sensitization caused by sudden release of active ingredients.

[0045] refer to Figure 3This figure visually demonstrates the skin barrier repair effects of different formulations. The TEWL reduction rate in all three examples exceeded 30%, significantly higher than that of Comparative Example 1, Comparative Example 2, and the mineral oil control group. This indicates that the biomimetic sebum film base oil combined with ceramide NP can effectively fill the lipid gap in the skin interstitial matrix, reduce skin moisture loss, and maintain the integrity of the skin barrier. Comparative Example 1, lacking ceramide NP, showed a TEWL reduction rate of only 11.7%, confirming the core role of ceramide NP in barrier repair and addressing the shortcomings of existing mineral oil-based protective products, such as poor compatibility with children's sebum, damage to the skin barrier, and poor water-locking effect.

[0046] refer to Figure 4 This figure visually presents the sensitization risk of different samples. The SI value of Example 2 is 1.3, which is close to the SI value of the negative control pure squalane, and far below the positive threshold of 2.0 specified by the OECD 442E standard, and also far below the 2.8 of Comparative Example 2. This proves that the sensitization risk of the formulation of this invention is extremely low and meets the safety requirements of children's skin care products. Comparative Example 2 did not use nano-encapsulation technology, and the active ingredient directly contacted a large amount of immune cells, resulting in an SI value exceeding the positive threshold. This confirms that the solid-liquid dual sustained-release system combined with defuranocoumarin essential oil can effectively reduce sensitization, solving the defects of existing plant essential oil-based protective products with high sensitization risk and easy induction of photosensitive dermatitis.

[0047] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A hypoallergenic, non-irritating outdoor protective essential oil for children, characterized in that, The invention comprises a biomimetic sebum film base oil and a solid-liquid dual sustained-release system dispersed in the biomimetic sebum film base oil; the biomimetic sebum film base oil comprises refined squalane, cold-pressed camellia seed oil, jojoba oil and ceramide NP; the solid-liquid dual sustained-release system uses behenic acid glyceride and cetyl palmitate as composite wall materials to encapsulate defuranocoumarin lemongrass essential oil and real lavender essential oil to obtain solid lipid nanoparticles, the particle size of which is 150nm~250nm.

2. The hypoallergenic and non-irritating outdoor protective essential oil for children according to claim 1, characterized in that, The mass of the ceramide NP accounts for 0.5% to 1.5% of the total mass of the biomimetic sebum film base oil.

3. The hypoallergenic and non-irritating outdoor protective essential oil for children according to claim 1, characterized in that, The mass ratio of refined squalane, cold-pressed camellia seed oil, and jojoba oil is 1.2~2.4:2.3~3.2:2.1~3.

3.

4. The hypoallergenic and non-irritating outdoor protective essential oil for children according to claim 1, characterized in that, The mass ratio of behenicol glyceryl ester to cetyl palmitate is 2~3:

1.

5. The hypoallergenic and non-irritating outdoor protective essential oil for children according to claim 1, characterized in that, The mass ratio of the defuranocoumarin citronella essential oil to the real lavender essential oil is 1.5~2.5:1, and the total mass of the defuranocoumarin citronella essential oil and the real lavender essential oil accounts for 15%~25% of the total mass of the solid-liquid dual sustained-release system.

6. The hypoallergenic and non-irritating outdoor protective essential oil for children according to claim 1, characterized in that, The solid-liquid dual sustained-release system accounts for 8% to 15% of the total mass of the protective essential oil.

7. The hypoallergenic and non-irritating outdoor protective essential oil for children according to claim 1, characterized in that, The sensitization activation index (SI) of the protective essential oil is characterized by being significantly lower than the positive threshold of 2.0 in the OECD 442E standard.

8. A method for preparing a hypoallergenic and non-irritating outdoor protective essential oil for children, used to prepare the hypoallergenic and non-irritating outdoor protective essential oil for children as described in any one of claims 1 to 7, characterized in that, Includes the following steps: S1. Weigh out refined squalane, cold-pressed camellia seed oil, jojoba oil and ceramide NP according to the formula, mix them evenly to obtain biomimetic sebum film base oil, sterilize and set aside. S2. Weigh behenic acid glycerides and cetyl palmitate according to the ratio, heat to a molten state, add soybean lecithin accounting for 2%~5% of the total mass of the oil phase wall material, mix evenly to obtain an oil phase wall material containing emulsifier, add defuranocoumarin lemongrass essential oil and real lavender essential oil to the oil phase wall material, stir evenly to obtain a mixed oil phase. S3. Add the mixed oil phase to the phosphate buffer solution preheated to the same temperature, and disperse it by high-speed shearing to obtain the primary emulsion. Then, perform high-pressure homogenization on the primary emulsion to obtain a solid lipid nanoparticle dispersion, and freeze-dry it to obtain solid lipid nanoparticle powder. S4. Add solid lipid nanoparticle powder to biomimetic sebum film base oil and stir to disperse evenly; S5. The evenly dispersed protective essential oil is filtered through a 0.22μm hydrophobic polytetrafluoroethylene microporous membrane for sterilization to obtain the finished product.

9. The method for preparing hypoallergenic and non-irritating outdoor protective essential oil for children according to claim 8, characterized in that, The heating temperature in S2 is 75℃~85℃; the preheating temperature of the phosphate buffer solution in S3 is no more than 2℃ different from the temperature of the mixed oil phase; the high-speed shearing speed is 8000rpm~12000rpm; and the shearing time is 3min~5min. The hydrophobic microporous filter membrane in S5 is made of polytetrafluoroethylene.

10. The method for preparing hypoallergenic and non-irritating outdoor protective essential oil for children according to claim 8, characterized in that, In S3, the high-pressure homogenization pressure is 800 bar to 1200 bar, the homogenization cycle is 3 to 5 times, the cold trap temperature for freeze drying is -45℃ to -55℃, and the drying time is 24h to 36h; in S4, the stirring and dispersion speed is 300 rpm to 500 rpm, the dispersion time is 10 min to 15 min, and the system temperature during the dispersion process is controlled at 20℃ to 30℃.

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