During our earlier work on photodynamic states in white mice, we became interested in the possibility that the systemic effects of photodynamic action might be related to the release of histamine. The role of histamine in the production of the local and systemic changes resulting from photodynamic action has not been defined adequately, and yet it is not uncommon to find antihistaminics recommended for the treatment of photosensitive states.12
In an earlier communication we reported the failure of pyrilamine maleate (Neo-Antergan) and epinephrine to alter the effects of the photodynamic action produced by a hematoporphyrin derivative and visible light in white mice.10 It seemed to us that our inability to alter the shock-producing mechanism by these 2 drugs, especially by pyrilamine, casts considerable doubt on the idea that histamine is the major agent in the production of shock by a photodynamic process. Some definite experiments were devised to