A University of Guelph Equine Research Centre (ERC) study indicates that flaxseed (linseed) can relieve symptoms of sweet-itch, an allergic skin condition more formally known as recurrent seasonal pruritis. Sweet-itch is a common complaint in many parts of the world. As many as 60% of horses in Queensland, Australia, are affected; more than 21% of horses in Israel; 26% of horses on the northwest coast of North America; and nearly 5% of horses in Japan.

Sweet-itch is triggered by the serum of tiny biting flies known as midges or no-see-ums (genus Culicoides). The bites cause intense itching, skin irritation, and patchy hair loss in horses. In North America, some 20% of imported Icelandic horses suffer from sweet-itch, largely because those horses build up no immunity to the fly bites in their native Iceland.

A study performed at the ERC demonstrated that flaxseed (linseed), fed as an oral supplement, can provide relief from the symptoms of allergic skin conditions. Flaxseed has long been recognized as a superior vegetable source of omega-3 fatty acids to treat many atopic (allergies likely to be hereditary) skin diseases in dogs. But while it is commonly fed to horses to improve the hair coat, the exact effect of these omega-3 fatty acids on the equine dermis (skin) is unknown.

In the ERC’s double-blind study, six Icelandic horses with a history of sweet-itch (confirmed by a skin test with Culicoides extract) were fed ground flaxseed, or an equivalent amount of bran meal as a control, for 42 days. On Days 0, 21, and 42, the horses were injected with Culicoides extract, saline (as a negative control), and histamine (as a positive control, guaranteed to trigger a skin reaction), and the resulting reactions were assessed over a period of 18 hours. Samples of skin, blood, and hair were also taken to provide a fatty acid profile.

Horses on the flaxseed supplement showed significantly smaller skin test re