Lodoxamide is an antiallergic compound. The present study evaluated the efficacy on clinical and cytological parameters and safety of topical lodoxamide compared to placebo in the treatment of allergic conjunctivitis. The trial, designed as double-blind, randomized, placebo-controlled and parallel group treatment, was carried out in 30 patients, suffering from seasonal allergic conjunctivitis due to grass pollen, during the pollen season. Patients received lodoxamide tromethamine 0.1% eye drops or placebo eye drops, one drop in each eye t.i.d. for 4 weeks. The clinical and cytological evidence was investigated by clinicians on admission and after 4 weeks' treatment. At the end of the trial, only the lodoxamide-treated group showed a significant clinical improvement, associated with a reduction of inflammatory cells. No serious side effects were observed. The results show the clinical efficacy of lodoxamide in the treatment of pollen-induced allergic conjunctivitis. In addition, lodoxamide exerts its antiallergic activity by reducing inflammatory infiltrate (mainly eosinophils).