Abstract: Methods for treating and preventing late-phase allergic reactions with misoprostol in a pharmaceutically acceptable excipient are provided. Tablet forms of misoprostol may be administered at doses of between 100 .mu.g and 300 .mu.g. The preparation may be administered alternatively as an aerosol. Late-phase respiratory and cutaneous reactions to dust mites, food and occupational allergens, pollen, weeds, grass, drugs, animal dander and chemicals may be treated with the described misoprostol-containing agents. Urticaria, contact dermatitis, asthma, allergic rhinitis and anaphylaxis are conditions which may be treated according to the presently disclosed methods and pharmaceutical agents.