The paper provides the results of experimental risk assessment of exposure to a biological factor combined with a chemical factor, which present with the protein-bearing dust and sulfur dioxide. The regularities and specific features of the functioning of the body's physiological systems have been revealed in the development of responses to combined exposure to biological and chemical factors, which show that the response may take three basic paths: sensitization, allergopathy, and toxic allergopathy. The essentials of the methodology evaluating and predicting the nature of the biological effects of a response in the experimental study of combined exposure to biological and chemical factors of the nature have been developed.