Abstract
A general survey is given of the chemistry and properties of the allergens causing bronchial asthma, eczema, and hay fever in "atopic" patients. The carrier molecules of, for example, the ubiquitous house-dust allergens are chemically unrelated structurally, though various allergens incorporate common structural sites of lysine--sugar conjugation. These sites probably activate a multi-enzyme system mediating allergic reactions and involving components of human complement. This process is non-immunological; the proposal is made that this mediator system is intrinsically more sensitive to nonspecific stimulation in allergic persons.