As first used by Pirquet, the term allergy was meant to apply to all forms of altered reaction capacity of cells. Subsequently, it was applied to all forms of hypersensitiveness, that is, clinical reactions allied to anaphylaxis in which an antigen-antibody mechanism either had not been demonstrated or had not played a rôle. The word itself means nothing more than altered reaction. In this comprehensive meaning it has also been used to describe the phenomenon of altered reactivity, the cause of which is unproved. Thus there are recorded the terms "physical allergy," "climatic allergy," and in this connection, the term "emotional anaphylaxis" may be mentioned.
A discussion of the dermatologic aspects of allergy in the broad meaning of the term would embrace a considerable number of cutaneous diseases and cutaneous reactions. For example, all types of eczema, since this disease manifests altered reactivity of the skin and blushing, could be
JOSEPH V. KLAUDER. CLINICAL ASPECTS OF ALLERGY IN DERMATOLOGY. Arch Derm Syphilol. 1929;19(2):198–225. doi:10.1001/archderm.1929.02380200026002