The reactivity of horse skin to intradermal inoculation of histamine, serotonin and bradykinin was investigated, and the resulting reactions compared with those produced in the same horses by a 1% whole‐body extract ofCnliroides.Both histamine and bradykinin produced large reactions, but there was no significant correlation between the dermal responsiveness to insect allergen and either histamine or bradykinin. Two anti‐hislamine drugs (promethazine hydrochloride and tripelennaniine hydrochloride) were effective in reducing the reaction produced by the insect extr