Horse Health: Sweet Itch

horse with sweet itch

Sweet Itch is a seasonal dermatitis condition that has bedeviled horses and their owners for centuries. It is actually a hypersensitivity or allergic reaction to the saliva of Culicoides midges or other biting insects seen mostly in the summer. Related to flea bit dermatitis in dogs, it causes the horse to swell at the site of the bite. The swelling area itches, and the horse begins to rub or chew until the hair is gone and the skin begins to break down into patches of raw lesions. When flies land on the raw areas, they deposit bacteria and contaminates which then cause a secondary bacterial infection of the skin, further aggravating the situation.

The condition frequently goes away in the winter months when insects are at a low. However, during the Spring and summer it can be truly miserable. Unfortunately, it also seems to get worse with age as tolerance begins to wane and the immune response gets more and more exaggerated.

Most frequent signs are the rubbing away of mane and tail hair down to a grey layer of skin that looks a little like elephant hide. If the problem gets as bad as the horse pictured, the hair loss can be permanent.

Of course, the first order of business is to stable the horse in an area where the offending insects cannot bite: In a clean paddock with strong wind or a clean stall with screens on the openings and a fan that prevents the flies from flying and landing (They cannot combat swift air currents). Use fly masks or even whole “fly net blankets” and fly sprays to prevent the bites.

more horse with sweet itch

A variety of corticosteroids and antihistamines, especially hydroxyzine, are useful in controlling the extreme reactions and miserable itching, but their side effects (including immune suppression) can also be very damaging. Other immunotherapy products appear to have a positive effect, but most are not available in the US or used off-label. (Find information on Low Dose Naltrexone and allergies in pets. It has worked miracles with dogs who develop allergies to flea bites).

Soothing Shampoos which contain Calloidal Oatmeal, Tee Tree Oil, and Aloe can help to soothe the skin and temporarily alleviate some of the itch, but their use is purely symptomatic, not curative, and their effect is very short term.

The sad reality is that the only truly effective treatment at this time is prevention. Many times, an afflicted horse who lives in a particularly warm and moist climate can be moved to a colder climate and live a happy life again free of symptoms.

It is not a good idea to breed horses that develop this condition as the pre-disposition to this allergy is genetic and often shows up in offspring. Certain breeds of horses appear to be afflicted more than others – again probably because of the smaller gene pool in purebred animals and the genetic basis of the hypersensitivity. Whole lines can be bred from horses who are not regularly exposed to the parasite thus masking the condition until one of the offspring goes to a warmer climate or area where it becomes exposed and shows the problem.

Persons purchasing a horse in the winter months should also be aware that the condition is frequently not visible at that time and might want to inquire about its condition in the summer months.

Please note that this advice is neither veterinary nor prescriptive in nature but offered only as an introduction to this topic.

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One thought on “Horse Health: Sweet Itch

  1. Be sure that you do not confuse Sweet Itch with Rain Rot (Rain Scald). We are treating a pony right now for a severe case of Rain Rot that looks like these pictures. (It is the most severe case we have ever seen) I will post pictures of her in the next few days on the Rain Rot Post. Read What is Rain Rot

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