Please help! what is the most effective anti-allergy otc pill?

Several: Several otc medications you can get to treat your allergy symptoms. They all contain antihistamine. Some have fast onset but does not last long (benadryl) and also cause drowsiness. The second generation antihistamine last longer and does not cause drowsiness like zyrtec, allergra, claritin, (loratadine) of which Claritin (loratadine) has the longest onset. Seek specialist help from an allergist if your symptoms are severe.