The invention relates to 
medicine and veterinary science and can be used for treating diseases associated with changes of the qualitative and / quantitative composition of blood 
extracellular DNA, namely generalised infection diseases provoked by 
bacteria, diseases provoked by fungi and 
protozoa, atherosclerosis, pancreatic diabetes, allergic diseases associated with 
delayed response hypersensitivity and diseases due to 
somatic cell gene mutations. The inventive method for treating diseases associated with modifications of the qualitative and / or quantitative composition of blood 
extracellular DNA, namely generalised infection diseases provoked by 
bacteria, diseases provoked by fungi and 
protozoa, atherosclerosis, pancreatic diabetes, allergic diseases associated with 
delayed response hypersensitivity and diseases due to 
somatic cell gene mutations consists in injecting an agent destroying blood 
extracellular DNA. DNAse 
enzyme injected into a 
systemic blood circulation in doses which modify the electrophoretic profile of the blood 
extracellular DNA definable by pulse-
electrophoresis can be used in the form of an agent destroying said blood 
extracellular DNA. Said DNAse 
enzyme can be injected in doses and at regimes ensuring the level of a 
blood plasma DNA-hydrolytic activity which is measured in the 
blood plasma and is higher than 150 Kunz units per litre of 
plasma during a total time higher than 12 hours a day. The inventive method makes it possible to develop a high-efficient and low-toxic method for treating diseases associated with modifications of qualitative and / or quantitative composition of blood 
extracellular DNA individually or in combination thereof.