Understanding summer eczema — the mechanism behind the itch
A hypersensitivity to Culicoides saliva, not a cosmetic flaw. What lies behind the clinical picture and which levers the management knows.
Equiterna Redaktion
Veterinarian · Sports medicine
Summer eczema is not a mere skin irritation, but an allergic disease. The trigger is the saliva of small biting midges of the genus Culicoides: in predisposed horses the immune system reacts to it with an immediate-type hypersensitivity (type I hypersensitivity), often accompanied by a delayed component.
The result is a tormenting itch, above all at the crest, tail dock and ventral midline. Through rubbing, scales, bald patches and thickened skin areas develop. The mechanism also explains the seasonality: with the flight period of the midges from spring to autumn, the symptom picture stands and falls.
Why Icelandics are particularly affected
Striking is the clustering in horses imported from Iceland. The reason is the so-called import effect: in Iceland, Culicoides midges practically do not occur. Horses born on the island therefore grow up without early allergen contact. If they are exported as adult animals to the mainland and exposed to the midges there for the first time, a considerable proportion develops summer eczema.
Remarkable: Icelandics born in Europe do not fall ill more often than other breeds. So it is less a pure breed predisposition than the interplay of genetic predisposition and missing early-childhood allergen imprinting. That makes the distinction important before one speaks of a breed problem.
“It is not the horse that is wrongly bred. As an adult it meets for the first time an allergen it never knew in its homeland.”
Management means exposure protection
The guiding principle is not cure, but the reduction of midge contact. Close-fitting eczema rugs with belly and neck protection form a physical barrier. Midges are most active at dusk, which is why grazing times are shifted to midday and wind-exposed paddocks away from wetland biotopes are preferred. A consistent, gentle skin care keeps the irritated skin surface stable.
At the feeding level, support is considered via the skin barrier. Long-chain omega-3 fatty acids (such as from algae oil) and their plant-based precursor from linseed are investigated in connection with skin inflammation and barrier function; zinc is a cofactor of numerous enzymes of skin regeneration. These are nutritional building blocks of skin health — no treatment of the allergy.
Context: an existing or suspected allergic skin disease belongs in veterinary clarification. Rugs, pasture management and ration building blocks accompany a veterinarily supervised concept, they do not replace it. There are no healing promises here.
Sources
Compounds in this article
Usage note
This content is for information and education. It does not replace veterinary diagnosis or treatment. If your horse shows signs of illness, consult a veterinarian.
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