Horse Summer Dermatitis
May 05, 2011
"Sweet…", as a modern term, denotes pleasure and
enjoyment. However, for a horse, sweet itch can be anything
"Sweet Itch, also known as summer eczema or equine dermatitis,
is one of several seasonal allergies that your horse may
encounter," notes Dr. Glennon Mays, clinical associate professor at
the Texas A&M College of Veterinary Medicine & Biomedical
"Equine dermatitis can have varying causes," explains
Mays. "Allergens may irritant your horse's skin, but viruses
and bacteria may also manifest themselves as dermatitis.
These foreign agents can cause inflammatory conditions in the skin
and may affect your horse's hair coat. Equine sweet itch is a
seasonal allergic skin condition that can be caused by fly bites or
midge bites. Horses that suffer from sweet itch have
developed an allergy to these bites."
Insects flourish in the summer and horses may have sensitivities
to insect bites, notes Mays. In particular, black flies,
known as buffalo gnats, can seek horses as hosts. These flies
feed on the blood of mammals and are attracted to hosts by smell,
heat and sight. They prefer the host's head, hair and ears
but will also bite any skin that is exposed.
"The female black flies are blood feeders," explains Mays.
"The fly bites by cutting into the skin and feeding on the pooled
blood. Anticoagulants injected into the feeding sight cause
an allergic reaction."
Black flies feed during the day, so stable animals during the
day when fly populations may be more abundant. Fly repellents
applied to the chest, belly and ears can be effective if applied
daily, says Mays. Cloth coverings fitted over horses' ears
may be used for additional protection. Coverings may also be
used to protect your horse's eyes and head.
"Allergic dermatitis can result from the black fly bite," states
Mays. "Antigens in their saliva can cause allergic
reactions. Additionally, the black fly bite can become
painful and itchy as blisters form. Therefore, protecting the
face and ears from flies eliminates a major source of irritation
for your horse."
Equine dermatitis will usually result in symptoms such as
scratching, biting affected area, crusts, hair coat damage or loss,
flaky dandruff and thickened skin, explains Mays. The itchy
skin can be further irritated when the horse rubs the area (on
fences or stalls) to the point of hair loss and scabbed skin.
This is when secondary bacteria can enter the skin and cause
"Sweet itch is commonly seen in 4 to 6 year old horses," notes
Mays. "Repeated exposure to the allergen, in this case, fly
bite, is required for the allergy to develop."
To help reduce the incidence of sweet itch, begin preventative
measures before fly season is in full force, suggests Mays.
Use a fan in your horse's stall. The constant airflow deters
flies from lighting and biting. If possible, place fine-mesh
screens over barn openings to prevent flies from entering
stalls. Install automated insecticide mist systems to help
control fly populations. Consult your local veterinarian for
the best insecticide to use in your stables and on your horse.
Black fly, stable fly, horse fly and midge bites all can cause
allergic skin reactions in horses. Corticosteroids are the
most useful treatment for controlling these skin allergies, notes
Mays. This anti-inflammatory helps stop the itching so that
the skin can heal. However, there may be steroid side-effects
in horses, so they must only be prescribed by your
If your horse has an annual encounter with summer sweet itch,
help him to manage the itch by taking preventative measures to
lessen the severity of an annoying allergy.
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