Sweet Itch in Horses: Causes, Symptoms, and Nutritional Support

If your horse spends the warmer months rubbing its mane, tail, or belly until the hair breaks or the skin becomes irritated, sweet itch may be to blame.

Sweet itch is more than occasional seasonal itching. It is an allergic skin reaction triggered primarily by the bites of Culicoides midges—tiny biting insects commonly called no-see-ums. For sensitive horses, exposure can lead to intense itching, inflammation, repeated rubbing, hair loss, and damaged skin.

Because sweet itch originates with an allergic response to insect bites, there is no nutritional ingredient that can simply make the condition disappear. Effective management usually requires reducing insect exposure while supporting the skin and the horse’s normal inflammatory response.

Understanding what is actually happening can help horse owners build a more effective management strategy.

What Causes Sweet Itch in Horses?

Sweet itch, also called insect bite hypersensitivity, occurs when a horse’s immune system overreacts to proteins in the saliva of biting insects, particularly Culicoides species.

Not every horse reacts this way. Two horses can live in the same pasture and encounter the same insects while only one develops significant symptoms.

In affected horses, insect bites trigger an exaggerated immune response within the skin. This produces inflammation and intense itching. The horse then scratches, bites, or rubs the affected areas, creating additional irritation.

This cycle can quickly become self-perpetuating:

Insect bite → allergic response → itching → rubbing → skin damage → more irritation

Breaking that cycle is one of the primary goals of sweet itch management.

What Does Sweet Itch Look Like?

Symptoms can vary between horses, but sweet itch frequently affects areas where biting midges feed and where horses can easily rub.

Common signs include:

• Persistent itching or rubbing
• Broken or thinning mane and tail hair
• Hair loss along the topline, mane, tailhead, or belly
• Dry, flaky, thickened, or irritated skin
• Small scabs or crusty areas
• Raw skin caused by repeated rubbing
• Restlessness when insects are active

Some horses experience relatively mild seasonal irritation, while severely affected horses may rub until significant areas of the mane or tail are lost.

Because several skin conditions can cause itching and hair loss, persistent or severe symptoms should be properly evaluated rather than automatically assumed to be sweet itch.

Why Sweet Itch Often Gets Worse During Certain Times of Year

Sweet itch is closely connected to insect activity.

Culicoides midges thrive in warm, humid environments and are particularly active around damp areas, standing water, manure, and decaying vegetation. Activity is often greatest around dawn and dusk.

For many horses, symptoms therefore become worse during warmer months and improve as insect populations decline.

In warm climates with long insect seasons, however, susceptible horses may deal with skin irritation for a significant portion of the year.

This is why management should ideally begin before a horse has rubbed its mane or tail raw.

Managing Sweet Itch Starts With the Insects

Since insect bites trigger the allergic reaction, reducing exposure is one of the most important components of management.

Depending on the horse and environment, management may include fly sheets or other physical barriers, appropriate insect repellents, fans in stalls, reducing standing water and damp organic material, and adjusting turnout during periods of peak midge activity.

A horse already experiencing severe itching may also require veterinary treatment to control inflammation, secondary skin infections, or other complications.

Nutrition should complement these strategies—not replace them.

Where Nutrition Fits Into Sweet Itch Management

This is where expectations matter.

A nutritional supplement cannot prevent every midge from biting a horse, nor should a supplement be expected to “cure” an allergic condition.

Instead, nutrition can help support the systems being challenged.

The skin is an active organ with substantial nutritional requirements. Maintaining its protective barrier, replacing damaged cells, growing healthy hair, and regulating normal inflammatory processes all depend on adequate nutrients.

For horses prone to seasonal skin irritation, nutritional support may therefore focus on several areas:

Omega-3 Fatty Acids

Omega-3 fatty acids are commonly included in equine skin supplements because of their role in maintaining healthy skin and supporting a normal inflammatory response.

The balance of fatty acids within the diet can influence inflammatory pathways throughout the body. Providing supplemental omega-3s can be particularly useful in equine diets that otherwise contain relatively little.

Omega-3 supplementation does not eliminate the allergic trigger behind sweet itch, but it can be one piece of a broader nutritional strategy for horses dealing with seasonal skin challenges.

Vitamin E

Vitamin E is an important antioxidant that helps protect cells against oxidative damage.

Horses with access to abundant fresh pasture may obtain substantial vitamin E naturally. Horses consuming primarily stored forage, or those with limited pasture access, may receive considerably less.

Providing adequate vitamin E supports normal immune function, muscle health, and cellular protection—including cells within the skin.

Zinc and Copper

Zinc and copper are trace minerals with important roles in skin integrity and hair growth.

Zinc contributes to normal skin repair, protein synthesis, and immune function, while copper plays a role in connective tissue formation and normal hair pigmentation.

More is not necessarily better. Trace minerals should be supplied in appropriate amounts and balanced within the total diet.

Biotin

Biotin is most often associated with hoof health, but its role in keratin production also makes it relevant to healthy skin and hair.

For horses that have rubbed out portions of their mane or tail, supporting normal hair production can be valuable as the underlying irritation is brought under control.

MSM and Turmeric

Ingredients such as MSM and turmeric are frequently incorporated into equine supplements designed to support normal inflammatory processes.

Neither should be considered a treatment for the allergic reaction responsible for sweet itch. Instead, they may complement nutrients such as omega-3 fatty acids, antioxidants, and trace minerals within a broader formula designed to support horses facing inflammatory and skin-related challenges.

Supporting the Skin From the Inside and Outside

Sweet itch management works best when approached from multiple directions.

Think of insect control as addressing the trigger, while nutrition helps support the horse.

Reducing exposure to biting midges may help decrease the number of reactions occurring in the first place. Appropriate nutrition helps provide the horse with nutrients needed to maintain healthy skin, support normal inflammatory processes, and regrow healthy hair.

Neither strategy necessarily replaces the other.

For a horse that struggles every summer, waiting until the mane and tail are already damaged can make the season considerably harder to manage. Proactive insect management combined with consistent nutritional support before and throughout insect season may provide a better foundation.

Where Soothe & Shine Fits

North Star Animal Nutrition’s Soothe & Shine was developed to provide comprehensive nutritional support for skin, coat, and normal inflammatory function.

The formula combines nutrients and functional ingredients including omega-3 fatty acids, vitamin E, MSM, turmeric, spirulina, zinc, copper, biotin, and postbiotics.

Rather than relying on a single “miracle” ingredient, Soothe & Shine takes a multi-nutrient approach to supporting the horse from within.

For horses prone to sweet itch or other seasonal skin challenges, it can be incorporated alongside appropriate insect-control and management practices to provide nutritional support for healthy skin and coat.

The Bottom Line on Sweet Itch

Sweet itch can be frustrating because the problem is not simply dry skin or a horse that happens to be itchy. It begins with an allergic response to insect bites, which means controlling exposure to those insects remains an important part of management.

But the condition also places considerable stress on the skin.

Supporting healthy skin, hair growth, antioxidant defenses, and normal inflammatory processes through appropriate nutrition can therefore be another valuable piece of the management plan.

The goal isn’t to find one ingredient that magically stops sweet itch.

It’s to reduce the trigger, support the horse, protect the skin, and interrupt the cycle of itching and rubbing before it becomes severe.

Frequently Asked Questions About Sweet Itch in Horses

Is sweet itch caused by sugar in a horse’s diet?

No. Despite the name, sweet itch is not caused by dietary sugar. It is an allergic reaction primarily associated with the bites of Culicoides midges and other biting insects.

Is sweet itch contagious?

No. Sweet itch is an allergic response and cannot spread from one horse to another. However, multiple horses living in the same environment may experience insect irritation, and more than one horse may be sensitive to insect bites.

Can supplements cure sweet itch?

No nutritional supplement should be expected to cure sweet itch. Supplements can provide nutrients that support healthy skin, hair growth, antioxidant protection, and normal inflammatory function, but reducing exposure to the insects responsible for triggering the reaction remains an important part of management.

When should I start managing sweet itch?

For horses with a history of seasonal sweet itch, management is generally easier when started before severe itching and rubbing begin. Insect-control strategies and consistent nutritional support can be established ahead of peak insect activity rather than waiting until significant skin and hair damage has already occurred.

Will the mane and tail grow back after sweet itch?

In many cases, hair can regrow once repeated rubbing and skin irritation are controlled and the hair follicles remain healthy. Regrowth takes time, making prevention of continued rubbing especially important.