Summer Sores In Horses: Frequently Asked Questions

What are summer sores? These painful sores are caused by parasite infestation and appear, as the common name indicates, during the warm summer months. You may also hear summer sores referred to as:

  • Granular dermatitis
  • Habronemiasis
  • Summer itch
  • Sweet itch
  • Jack sores

By any name, if left untreated, summer sores can cause severe problems. Read on to learn more about summer sores in horses.

What Causes Summer Sores?

sWhat causes summer sores

The main cause of summer itch is misplaced stomach worm larvae. These pests make their way to your horse’s skin in a complex and circuitous manner. Normally, stomach worm larvae, found in horse manure are picked up by flies and then deposited near the horse’s mouth when the fly lands there in the normal course of its daily activities.

At this point, the larvae enters the horses mouth and travels into it stomach where it matures into an adult stomach worm and lays eggs to start the whole process over again.

Problems arise when the larvae are left in some other moist area on the horse. For example, if the fly lands on an open wound and the larvae hops off there, it will begin to burrow into the raw flesh causing severe itching and inflammation.

A horse afflicted by stomach worms in this manner typically chews the itchiness and makes it much worse, attracting more flies and potentially more stomach worm larvae.

What Do They Look Like?

These gaping, angry looking sores may appear to be greasy because of the collected blood and lymph that drains from them. You may also see calcified white or yellow looking material that resembles rice. This is the start of proud flesh or scar tissue.

Why Do They Appear In The Summer Time

Why do summer sores appear in the summer time

Because the larvae are dependent on flies, and flies are only active during the warm weather months, that is when summer sores appear. Once fly activity dies down, the sores have a chance to heal and they do. It may also be that the larvae cannot survive on the outside of the horse’s body during cold weather.

Where Do Summer Sores Usually Occur?

Because the stomach worms’ larvae are attracted to dampness, summer sores appear on areas of your horse that may be naturally damp. They may occur around the eyes, nostrils, corners of the mouth, anus or vulva or on a stallion or gelding’s sheath. If your horse has a scratch, cut or other open sore that is attracting flies, it is very likely to become a summer sore.

How Can Summer Sores Be Treated?

How can summer sores be treated

A multipronged approach is necessary to treat summer itch. Keeping intestinal worms under control is important, so you should set up a regular deworming program for your horse. Choose a product that contains moxidectin or ivermectin as these ingredients are effective against stomach worms.

Simultaneously, you should treat the wound locally. Wash it thoroughly, daily with cool running water to reduce inflammation and keep it clean. You can try a soothing gel first (e.g. EQyss Micro-Tek Gel); however, if it’s not working, apply an antibiotic ointment containing DMSO (which will help it to be absorbed quickly and deeply).

It may be helpful to wrap the wound with clean, dry gauze to keep it clean and protected against flies and the horse’s chewing. In severe cases, your vet may wish to prescribe corticosteroids and antibiotics by injection or orally. If a great deal of proud flesh has formed, surgery or cryotherapy may be necessary.

Overall, keep flies under control. Keep manure cleaned up; manage your compost heap; add diatomaceous earth and/or insect growth regulators (IGR) to your horse’s feed; encourage the presence of beneficial fauna (e.g. parasitic wasps and harmless barn and garden spiders) around your barn and pasture to help keep flies under control.

Nicky Ellis
Nicky has been an editor at Horses & Foals since 2017. Horses have been in her life from her earliest memories, and she learned to ride a horse when she was 5. She is a mom of three who spends all her free time with her family and friends, her mare Joy, or just sipping her favorite cup of tea.


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