Benadryl. As stated before 1 25mg per 100 lbs. My 1000 pound arabian stepped in a ground wasp nest a couple of years ago. I gave him 10 capsules twice a day for a week (while also hosing his leg down etc.) Worked great, stopped him from scratching while his bites healed. I just put the whole capsules in his bucket with his sweet feed and he ate them right up! Oh, and he is allergic to most fly sprays also.