I recently encountered something similar with my 7 yr old 1/2 WB, 1/2 TB mare. She was abnormally cresty and “puffy” looking. In addition, she spent a lot of time rubbing her body on the fences, was very tight in her body, and had problems with frequent urination. I took her completely off alfalfa hay and all her supps and the condition reversed itself within 5 days. Reading more on equine food allergies I found that an allergy normally can only take hold if there is a compromise of the intestinal lining such as an ulcer or other irritation. Anyway, kept her on the Bermuda hay only diet for 4 weeks and slowly introduced her supplements and she has blossomed and no longer has the edema like puffiness, her tightness has disappeared, and her attitude has improved tremendously. I introduced a small bit of alfalfa and within 2 days she was starting to have problems again; alfalfa and alfalfa based products are off her menu from now on. I’m discovering a lot of the issues we have with our horses is greatly related to nutrition and reactions to their feed can create a number of issues. Good luck in your quest to help your horse.