3 Most Common Skin Diseases of Spring

Spring is in the air, but with the warmer weather comes insect infestations and lots of itching. Let’s check out the top 3 culprits for spring skin diseases.

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Sweet Itch

The most common insect hypersensitivity is caused by the tiny insect Culicoides. Sweet itch occurs in horses of all breeds and ages, but studies have shown it is more common in Icelandic ponies, Haflingers and Friesians. It is rare in Thoroughbreds. It’s a disease more common in young horses, but can be triggered by stress in the older crowd.

Tell me about Culicoides.

This bug is better known as a “biting midge” or “no-see-um.” They are weak fliers, breed near standing water and are most active during dusk and dawn. They love warm, humid weather. They can survive a frost, but not a prolonged drought.

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What Should I Look For?

  • Intense itching – particularly around the head, neck, withers, under the belly, and around the base of the tail
  • Bald, inflamed, crusty areas with some scabbing
  • Hair loss with flaky dandruff
  • Temperament changes during riding – ranging from lack of focus and lethargy to agitation and impatience
  • Excessive head shaking
  • Restlessness

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Photo Source British Horse Society

What Can I Do?

  • Fly control is the only treatment for sweet itch, so keeping a clean stable is a priority.
  • Stable indoors during dusk and dawn.
  • Keep your horse away from standing water and mow any long grass surrounding ponds or creeks.
  • Provide a fan when stalled.
  • Fly sheets, masks and boots help once the initial itching is relieved.

If the itching becomes chronic, your veterinarian can prescribe a short-term steroid medication and antihistamine.  There is some evidence that feeding MSM or Omega-3 fatty acid supplements help.


Scratches is a common skin disease that effects the heels and pasterns. In varying forms it’s also known as greasy heel, mud fever, dew poisoning, pastern dermatitis and pastern folliculitis. Bacteria and fungi are usually involved, but the main factor is repeated wet/dry conditions that weaken the skin.

What Should I Look For?

  • Reddened patches of skin
  • Oozing yellowish liquid
  • Hair loss
  • Hard crust or scabs
  • Area may be sensitive to touch
  • Lameness can result in severe cases

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What Can I Do?

  • Gently remove all crusts, scabs and dead tissue with a mild soap.
  • Dry throughly.
  • Clip hair away from the area as needed.
  • Apply ointment and medication as recommended by your veterinarian to treat the secondary infection.
  • After healing, petroleum jelly can be used as a barrier cream for horses grazing in muddy, wet pastures.

It is important to diagnose exactly what has infected the weakened skin before medicating. Choices include antibiotic, antifungal, and steroid treatments. To give you an example of the many different treatments available, check out this “small” list:

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Source Vet Book

Rain Rot

Rain rot is a common skin infection also known as rain scald or streptothricosis. It is caused by the organism Dermatophilus congolensis and is not a fungal infection.

Tell me about Dermatophilus congolensis.

It is an actinomycete, which is an anaerobic bacterium with a branching growth pattern that colonizes through spores. The bacteria loves warm, damp weather and oxygen free environments.  The number one reason for rain rot infection in the spring is not removing excessive shedding hair.  The loose hair creates an oxygen free environment that builds up heat and moisture.

What Should I Look For?

  • Generally found on the neck, back and legs
  • Crusty scabs beneath the hair that are not itchy
  • Skin may be sensitive under heavy brushing or when scabs are removed

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Photo Source ‘Dermatophilus in a Horse: A Case Report’

What Should I Do?

  • Isolate the horse in a dry, clean area.
  • Use antimicrobial shampoo or Betadine on the infected areas daily for at least one week.
  • Dry the entire area after washing.
  • In severe cases, a veterinarian may prescribe antibiotics.

The bacteria is spread through contact, so disinfect all tack, equipment, and blankets.  Wash your hands frequently.

Go Riding!


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