Sweet itch, also known as summer eczema or Culicoides hypersensitivity, is one of the most frustrating skin conditions in horses. The first signs typically appear between May and September. This article explains where the condition comes from, why the gut plays such a central role, and how to support your horse through the season with targeted nutrition and supplements.
What is sweet itch exactly?
Sweet itch is not a skin disease, it is an allergic reaction. The horse responds with hypersensitivity to the saliva of Culicoides midges, small biting flies that are most active from dusk to dawn. Each bite delivers salivary proteins that a healthy horse would not even register. In a sensitive horse, those same proteins trigger an inflammatory cascade lasting hours to days.
The result is intense itching, especially on the mane crest, the tail base and the belly midline. The horse rubs itself raw, the skin breaks down, scabs form and hair falls out. In severe cases, open wounds develop and become secondarily infected.
Symptoms of sweet itch
- Intense rubbing against stable walls, fences or trees
- Bald patches at the mane crest, tail base and belly midline
- Crusting, flaking skin and small open wounds
- Restless behaviour at dusk and dawn
- Reduced appetite during peak periods
- Recurring patterns year after year, often starting earlier and lasting longer
The gut-skin axis: why nutrition matters
Research over the past decade shows that the skin and the gut are tightly linked through the immune system. A large share of the equine immune system sits in the gut wall. When the microbiota is out of balance, more inflammatory mediators reach the bloodstream, and these prime the skin to react more violently to allergens.
In practice: a horse with a healthy gut reacts less aggressively to midge bites than a horse with disturbed flora. This is no longer fringe theory. It is a mechanism discussed in mainstream veterinary literature on equine atopy. See also our article on gut health in horses for broader context.
Prevention: prepare the season early
Start in April, not in June. Waiting until the first crusts appear is too late. The immune system needs six to eight weeks to rebalance. Begin support by late April at the latest.
Limit midge exposure. Culicoides flies most actively at dusk and dawn and around standing water. Stable the horse from sunset to sunrise, fit fine-mesh stable fly screens and run powerful fans in the box. Midges are weak fliers and avoid air movement above 1 m/s.
Use a sweet itch rug for sensitive horses. A well-fitting eczema rug with belly flap and tail cover protects the high-risk zones effectively. Combine with a fine-mesh head mask during turnout.
Watch fructan peaks. Sugar-rich grass, especially during cold nights followed by sunny days, drives a fructan spike that disturbs gut flora. Restrict turnout in those periods or use a grazing muzzle.
Which supplements actually help
Probiotics and gut support. pH+ supports the gut microbiota and stomach pH balance, which feeds directly into skin resilience. Give daily from six weeks before the season at the latest.
Anti-inflammatory baseline. Tonic combines herbs and minerals that raise the general immune baseline. For horses with chronic eczema, lowering the background inflammation is a key target.
Omega-3 fatty acids. Linseed oil or a dedicated omega-3 supplement shifts the balance between pro- and anti-inflammatory prostaglandins. The skin becomes more resilient and the itch response milder.
Avoid doping-sensitive herbs. Some popular eczema herbs, such as high-dose nettle extracts, can cause positive doping tests in competition horses. See our guide to FEI doping-free supplements for safe selection.
When to call the vet
Call your vet when:
- Open wounds appear that do not heal within three days
- The horse develops a fever or eats noticeably less
- Swelling extends beyond the typical zones
- Conventional eczema management shows no improvement after three weeks
The vet can prescribe corticosteroids for acute peaks, or initiate hyposensitisation therapy where the horse becomes gradually less reactive to midge saliva via injections. Neither replaces structural prevention through nutrition and management.
Conclusion
Sweet itch is not an inevitable fate. With early prevention, smart management of midge exposure and targeted support of the gut-skin axis, the itching season can be reduced year after year. Start in time, think in seasons rather than peaks, and choose supplements that support the wider immune system rather than only suppressing the symptom.
Browse more articles in our knowledge base or read on about the role of the gut.