Why does my horse have crusty sores on its lower legs after fly season starts?

Read time: 3 minutes

Overview

Crusty sores on the lower legs after fly season starts are often linked to fly bites, skin irritation, or an early skin reaction that gets worse when insects are active. It can also happen if the skin is already damp, dirty, or rubbed, so there may be more than one reason at play.

It’s sensible to check the skin closely and keep an eye on whether the sores are small and dry, or whether they’re spreading, swelling, oozing, or making your horse uncomfortable.

Things To Check

1. Look at when the sores started and whether they appear after turnout, especially near fields with more flies or midges.

2. Check whether the lower legs are itchy, warm, swollen, or being stamped, rubbed, or nipped at more than usual.

3. Inspect the sores for crusting, broken skin, discharge, scabs, or any obvious bite marks.

4. Check whether the skin is wet, muddy, greasy, or caked with dirt, as that can make irritation harder to settle.

5. Look at whether the problem is on one leg or several, and whether it is only on the lower limbs.

6. See if your horse has a history of summer skin sensitivity, sweet itch, or reactions to fly bites.

7. Notice whether the sores are getting larger, more numerous, or starting to look sore and painful.

Common Causes

Fly bites and midge irritation are common triggers once fly season begins. Some horses react with small crusty sores where the insects bite, especially on the lower legs where the skin can be more exposed.

Simple skin irritation from mud, sweat, wet turnout, or frequent rubbing can also make the area sore and scabby. If the skin barrier is already irritated, flies may make the problem more noticeable.

Less commonly, there may be a summer skin condition such as sweet itch, a bacterial skin infection, or another type of dermatitis. These can look similar at first, which is why it helps to monitor the pattern rather than assume one cause.

What To Do

Gently clean the area if needed, then dry it well. Avoid harsh scrubbing, because that can make the skin more irritated.

Try to reduce fly exposure as much as you reasonably can by changing turnout timing, using shelter where possible, and keeping the horse’s environment as clean and tidy as practical.

Monitor the sores over a few days. If they are staying small and dry, that may fit with minor irritation, but if they are spreading or the skin is becoming more inflamed, it’s worth getting the horse checked.

Keep notes or photos so you can compare how the legs look day to day. That can help you spot whether the issue is settling or becoming more active.

Products That May Help

For horses that seem more bothered by flies and summer irritation, a fly-season routine can be useful as part of day-to-day management alongside cleaning and monitoring.

Horse Fly Sprays & Summer Care

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