Fighting allergies is very frustrating. Unfortunately, we never really cure allergies but we can find ways to manage them.
Horses can be allergic to a variety of things but Culicoides species, which cause sweet itch, can be particularity aggravating.
Looking at how Culicoides feed can help formulate the best defense plan.
Usually the males just hang around the horse waiting for the females. After breeding, the females need a blood meal to finish the life cycle and lay their eggs. One bite from a midge can raise the histamine levels (what causes itchiness) for 1 hour before returning to normal. This is the immediate reaction.
Some horses also have a delayed itchy reaction to the bite. One night of midges’ unrestricted access to an allergic horse can take 3-6 weeks to resolve ... even if the horse receives no new bites.
That is why it is important to have the best control possible.
A good study about sweet itch in horses in British Columbia gives us some other clues. The midges prefer certain areas on the horse:
Image source: The Hypersensitivity of Horses to Culicoides Bites in British Columbia, Gail S. Anderson, Peter Belton and Nicholas Kleider, Can Vet J Volume 29
We think that they land in these areas and climb down the hairs to the skin. Then the female will bite multiple times during the 5-10 minute feeding period per midge.
We need to really concentrate on protecting these areas.
Clinically, I've found that for an allergic horse, it is best to start with twice-a-day treatments focusing on these regions. Sometimes using a soft cloth or mitt allows for a more effective way to apply Ecovet. On the tail head, mane and withers, I have advised some clients to use the stream setting on the bottle to penetrate these areas more effectively.
Other tips include stabling at night if possible and using fans in the stall areas because midges are weak fliers. Once the allergic reaction starts, contact your veterinarian to discuss ways of deceasing the severity of the allergic reaction.
As they say, an ounce of prevention ...