Flaxseed Might Help Fight Sweet-Itch

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 reactions to Culicoides serum after 42 days, indicating a less severe allergic response. Researcher Wendy Pearson O'Neill, MSc, also noted a reduction in the long-chain saturated fatty acids in the analyzed hair, which she says is an indication of changes in secretions from the skin. "By altering the fatty acids in the skin secretions, it's possible that certain populations of dermal microflora were affected, changing their ability to metabolize compounds such as histidine and trans-urocanic acid, which are involved in immune function," she explained. "This would reduce the overall immune response to Culicoides injection."

There were no significant changes in the fatty acid profiles of the skin or blood in treatment or control horses, and blood counts and biochemistry panels remained within the normal range. The ERC team concluded that flaxseed as an oral supplement is well-tolerated by horses, has no adverse side effects, and has considerable potential as a treatment for allergic skin disorders.

About the Author

Karen Briggs

Karen Briggs is the author of six books, including the recently updated Understanding Equine Nutrition as well as Understanding The Pony, both published by Eclipse Press. She's written a few thousand articles on subjects ranging from guttural pouch infections to how to compost your manure. She is also a Canadian certified riding coach, an equine nutritionist, and works in media relations for the harness racing industry. She lives with her band of off-the-track Thoroughbreds on a farm near Guelph, Ontario, and dabbles in eventing.

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