Proxicromil is substituted chromone patented in the late 1970s by Fisons Ltd. for the treatment of allergic asthma. Proxicromil acts on to FcεRIreceptor in mast cells, thereby inhibiting the production of histamines. Proxicromil is tested through a variety of independent studies for its beneficial effect as an anti-allergen, its efficacy against migraine, asthma and tumor enhancement. It shows no effect as a prophylactic against migraine. The reported side effects during this study related mainly to transient gastrointestinal troubles and were generally of a mild nature. For asthma and exercise-induced bronchospasm, Proxicromil was found to be mildly effective. But the investigation was discontinued when malignancies occurred in long-term animal studies.