We bought 2 horses last July 2010 - my walking horse 5 yrs. Old and my stepdaughter's 9 yr. Old paint. By December I started noticing my walking horse kept rubbing his butt like we hadn't wormed him, so I wormed him . . . Again. I kept noticing that week after week he kept rubbing his butt. Rubbing to the point that he rubs both sides of his cheeks bare and some raw spots but doesn't really rub the hair off his tail bone, so I wormed him again. Within a 3 month period I wormed him every month. Finally, realizing that perhaps there is more of a problem consulted a veterinarian who suggested that he has might have an allergy, perhaps to Bahia grass/seedlings, which is a very common grass in our area. We started him on TriHist, an antihistamine. Victory . . . This seemed to cure the problem. Each day I added the antihistamine to his feed and he stopped the rubbing. But then, we went on vacation and took our horses to TN for a week, which mean't he had a nice stall at night, versus just being out to pasture at home in MS. All the while, continuing with the antihistamine, and actually he got it twice a day while on vacation instead of just once a day. By mid week he had rubbed his butt bare and raw again and now that we have been home it is still continuing. I am totally at a loss. Has anyone had this problem, seen this problem, have any suggestions. We don't have deep pockets to go through a slew of expensive tests. I am really not sure where to go from here.