What you see. The starting point for addressing any equine health related issue is your observation.


Flies Bothering or Biting Horse


Black flies, horse flies, deer flies and horn flies are all blood-sucking biting flies that cause horses pain, irritation and can cause allergy (hypersensitivity). Stable flies do not bite but are irritating and annoying to horses. Biting flies and others have the potential to spread certain diseases. Each of these flies has its own unique life-cycle and feeding characteristics but, generally, they are all active during the warmer months, and they tend to favor areas close to water.

In severe cases, these insects can cause severe irritation or an allergic response, usually in the form of hives.

  • Code Green

    Contact Your Vet to Obtain Useful Advice & Resources
    • To discuss your equine's general health and management.
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your role


What To Do

Check your horse carefully for areas of hives, hair loss, dandruff, sores, redness, or swelling. If they appear bothered by these insects (itching, off feed, excessively anxious or upset), call your vet to discuss your findings and concerns. Treatment of the inflammatory response may be required.

Prevention is the best approach to dealing with biting insects. Depending upon the species involved, it may be best to house horses inside during the time insects are active. Use fans to blow air through stalls. Apply fly sprays, fly sheets, fly masks as needed.

Consider making environmental changes to reduce the fly population. Drain unused waterers and pools. Good manure management, combined with fly predators, feed through fly control, fly traps and fly lights- any and all may help reduce the stable fly population and lessen the problem with that species.

What Not To Do

Do not over-apply insecticide products, especially those in an oil base. Horses can be sensitive to these compounds and can have local skin reactions or worse.

your vet's role

Your vet may have some suggestions for management of the problem. If horses have problems with insect allergy, your vet will help you treat and manage that medically.
Questions Your Vet Might Ask:
  • Have flies been bothering the eyes?
  • What type of fly is creating the primary problem?
  • What have you tried for fly repellents?
  • Do you notice many small skin bumps over the body (hives)?
  • Are you seeing itchiness (rubbing or scratching)?
  • What preventative measures are you currently taking?

Author: Doug Thal DVM Dipl. ABVP