In the inter-war period physicians elaborated numerous ‘biotherapies’ grounded in the complex interactions between physiology, bacteriology and immunology. The elaboration of these non-specific biological treatments was stimulated by the theory of generalized anaphylaxis that linked the violent reaction to a foreign protein to a broad array of chronic diseases, from asthma and urticaria to rheumatism or chronic colitis. Such diseases were perceived as the result of an ‘abnormal reactivity’ to a sensitisation of tissues and organs by bacteria and by foreign (...) proteins, a view that provided an effective bridge between new concepts derived from bacteriology and immunology and the long-standing pathological tradition. Accordingly, physicians attempted to treat these conditions through specific desensitisation and non-specific biological therapies: peptone treatment, protein therapy, haemotherapy, ‘antivirus’ or ‘opotherapy’. Therapies that attempted to neutralise the harmful effects of chronic infections through ‘desensitisation’ were not seen as marginal medical practices, but were promoted by leading advocates of the ‘Pasteurian sciences’, such as Richet, Widal, Vallery-Radot, Wright and Fleming. They also led to development of new products by the pharmaceutical industry. (shrink)