This section is from the book "The Farmers Ready Reference Or Hand Book Of Diseases Of Horses And Cattle", by S. C. Orr. . Also available from Amazon: The Farmer's Ready Reference;.
When horses are highly fed on corn or other heating food there is often a severe itchiness of the skin which makes the animal almost frantic at times; he will bite his sides and rub himself against the side of the stall until the skin becomes bare and raw in places. There are no blisters or pimples at first, but just a severe irritation of the minute terminal nerves of the skin due to an over-heated, surfeited condition of the system from high feeding.
Treatment. - Change the feed if possible; give no corn; feed oats and bran and give carrots, potatoes, and any other vegetables that he will eat of a cooling nature. Give a heaping tablespoonful of Glauber's salt in the feed twice a day. Wash the body of the horse all over to remove the dirt from the skin, then sponge him all over with strong vinegar. The application of the vinegar should be repeated every day or two until the irritation ceases.