In contrast with exogenous allergy, the principal causal agents of which are inhaled, ingested, injected or contacted, the term endogenous allergy designates those hypersensitivities in which the allergens are formed within the body. The endogenous allergens may be divided, according to their origin, into two groups: the autoendogenous and the heteroendogenous. One speaks of autoendogenous allergens when autogenous substances (e. g., body cells and their products or tissue fluids) acquire antigenicity under certain conditions, which will be discussed in another part of the paper. Heteroendogenous allergens are foreign substances chiefly of proteinogenic nature which enter the organism from without but which call forth antibody formation only after their multiplication or growth within the body. The chief types of heteroendogenous allergens are bacteria, viruses, fungi and certain parasites, or their products.
For the sake of clarity, it is necessary at the outset to differentiate the endogenous allergens from those agents with