The effectiveness of cromolyn sodium in various clinical situations continues to expand. Ocular cromolyn has been utilized in allergic eye conditions, as well as vernal conjunctivitis, atopic keratoconjunctivitis and giant papillary conjunctivitis. Nasal cromolyn has been successfully utilized in the treatment of allergic rhinitis of the seasonal and perennial types, and oral cromolyn has been employed in people with multiple food allergies in an unusual condition such as systemic mastocytosis. There has been a reawakening of the versatility of this agent in view of its effective blocking of both early and late phase allergic reactions, and its anti-inflammatory potential. Truly cromolyn is a useful agent, not only for its therapeutic efficacy but for its virtual lack of side effects.