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What is Equine Recurrent Summer Dermatitis?

These bites are often caused by blood-feeding insects such as mosquitoes, midges of the Culicoides genus, flies, horseflies, and blackflies. The condition peaks between April and October due to favorable weather conditions for insects.

Culicoides are tiny midges (1–3 mm long) associated with aquatic and semi-aquatic environments. Their painful bites cause horses to itch in hard-to-reach areas, leading to irritation, fatigue, and a general decline in physical condition. These midges are also known vectors of parasites (like trypanosomes), so protecting horses from them is a wise precaution.

Not all horses are allergic to these bites. The tendency to react strongly seems to have hereditary roots, although no specific gene has been identified. Certain breeds are more predisposed, such as the Arabian Thoroughbred, Shetland, Welsh, Breton Draft, Connemara, Icelandic, and Friesian.

Dr. Dematteo, an equine veterinarian in Pacé near Rennes, also notes that dermatitis may be more prevalent in certain regions.
 
What Are the Symptoms of Dermatitis in Horses?

The first signs usually appear in a horse’s early years and worsen each spring, peaking in summer and subsiding in autumn. Symptoms can also appear in adult horses after major changes, like relocation.
Insects mainly target four areas:

• Head and ears
• Neck and mane
• Belly
• Base of the tail

Allergic horses develop a chain reaction after being bitten—both immediate (e.g., release of inflammatory agents) and delayed (e.g., migration of inflammatory cells into the skin). Symptoms can persist long after the bite.
The most striking symptom is intense scratching. To relieve the itching, horses rub vigorously against anything they can find (walls, trees, stall doors), roll on the ground, or even bite themselves. This leads to:

• Disheveled or bald patches in the mane and tail
• Enlarged lesions that may bleed
• Scales and thickened skin with color changes (hypo- or hyperpigmentation)

Secondary symptoms from scratching include:

• Skin damage
• Hair loss
• Epidermal tearing
• Scales and ulcers
• Thick, leathery skin

Alopecia (hair loss) is caused not only by scratching but also by inflammation in the hair follicle area. Simply preventing scratching is not enough and can cause stress, leading to other health issues.
 
Haarlem Oil for Summer Dermatitis
 
Therapeutic Properties:

• Anti-inflammatory: Reduces allergic skin reactions
• Natural antiparasitic: Helps repel insects from within
• Strengthens skin and hair: Thanks to sulfur, essential for keratin

How to Use:

• Apply the oil directly to affected areas once daily
• You can also soak a gauze pad for quicker, targeted action
• Repeat until the skin looks healthy and insects are no longer a concern

✅ Reported Effects (from user feedback):

• Less scratching
• Healthier skin
• Better hair regrowth
• Calmer, less stressed horse

Feel free to contact us for more information.