Treating Photodermatitis
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Sep 13, 2012
I am in need of your advice. I live in an area of Alabama where, unfortunately, we do not have an experienced equine vet.
I have a 12 year old splashed Overo paint mare. One afternoon she presented with drooling, staggering, and appeared to be in severe pain. She was given Banamine and stalled immediately (yes our pasture does have red and white clover). We noticed all of her white areas were raised/swollen and hot to the touch. She has been stalled during the day for the past 3 weeks and only allowed to graze at night. Her bald face was the first area to Scab and peel off. Now every splash where she is white is peeling off, even the white spots that are not exposed to the sun. The skin under the damaged peeling skin is very pink and has small white hairs growing back in. None of her sorrel areas are affected. The only conclusion I have come to is that she is suffering from photosensitivity. I am treating the areas with Vetericyn BID, Banamine as needed for pain, and penicillin only as needed for possible secondary infections. What would you recommend for bathing her? I don't want to use something too strong and further injure the new skin. Please help, any other suggestion, opinions and advice would be greatly appreciated.
Sincerely, Leslie
Dear Leslie;
Photosensitivity is a common problem with horses that a grazed on pasture with certain plants. As you mentioned in your letter, clover is among the toxic plants that can cause photosensitivity. Clover is especially common because horses will readily eat clover. The symptoms you describe are classic symptoms caused by ingestion of clover. You can learn more in our educational article about photodermatitis.
Unfortunately a horse that has intensive skin involvement may also have underlying liver disease. I would ask your veterinarian to consider testing for liver disease. I like the way you are treating the skin lesions, however you might consider topical steroids to help decrease the pain and inflammation. To prevent secondary infection penicillin would not be my first choice and I would never use an antibiotic on a hit and miss basis as described in your letter. You might consider a broader spectrum antibiotic such as Trimethoprim Sulfa. This antibiotic has the advantage of being broad spectrum and oral.
You can now eliminate clover and other toxic weeds from the pasture without destroying the entire pasture. Visit your local farm store to inquire about safe methods to control clover in your pastures.
Hopefully your mare can make a complete recovery and you can prevent such episodesin the future.
Robert H Koontz DVM
Chief Executive Officer
Conley and Koontz Equine Hospital Inc.
2249 South 500 East
Columbia City, IN 46725
877-499-9909
www.ckequinehospital.com