PROBLEM TO BE SOLVED: To provide an antiallergic agent excellent in safety and having less risk of side effects that prevents development of symptom of allergic diseases, particularly a type I allergic disease, and further improves and treats the symptoms.SOLUTION: The invention provides the antiallergic agent having preventing, improving and therapeutic effects on allergic disease, and having whole grass or a part of the Lactuca sativa var.asparagina as an active ingredient.