Photosensitivity - what is it?

Photosensitivity in horses - what is it?

Photosensitivity is a sensitivity to ultraviolet radiation. Often referred to as chemical sunburn, it is important to remember that photosensitivity is not the same as sunburn. Photosensitivity is a condition in which liver function is impaired and the liver is unable to break down toxic compounds.

Photosensitivity is seen in horses that graze and come into contact with plants that contain certain toxins that impair liver function by inhibiting the liver's ability to break down toxic compounds. A healthy and well-functioning liver will cleanse the blood of harmful substances. In photosensitivity, the horse loses the ability to break down certain toxic compounds that accumulate in the blood and get into the skin.

Symptoms of photosensitivity in horses

If your horse has photosensitivity, you'll notice a number of symptoms - but you'll need a vet to make the final diagnosis!

• The horse becomes restless when in the sun and will seek shade to a large extent.
• The skin becomes very itchy and may swell up - especially in exposed areas with a thin layer of hair.
• The most exposed areas are the muzzle, around the eyes, the base of the tail and legs with white markings.
• In the most affected areas, blistering, oozing sores and eventually scabs can develop.

Treatment and prevention of photosensitivity

If your horse has been affected by photosensitivity, you should put it in the shade indoors. The harmful light can penetrate through window glass, so don't place your horse near windows - even skylights.
The affected skin areas should be treated with a good moisturizing horse wound ointment, while exposed areas on the horse's legs can be shielded with bandages or fly masks.

The best way to prevent photosensitivity is to know your plants. Photosensitivity in horses is predominantly due to contact with specific plants, while only very rarely is the condition caused by medication.
The plants you should avoid having in your horse's paddock are:

• Alsike clover
• Wild parsnip
• Spotted knapweed
• Lupine
• Meadowsweet

In addition to paying attention to the plants in the paddock, you can apply sunscreen to the exposed and thin-haired areas.

Which horses are affected by photosensitivity?

Photosensitivity is typically seen in horses that graze on pasture. There are a number of plants in Danish fields that can damage the liver, causing harmful photodynamic substances to accumulate in the skin. If you have a horse with a thin layer of hair or a lot of white markings, you should also be aware of this.

Is your horse affected by photosensitivity? Riding Equipment recommends:

For the care and relief of the stressed skin: Silver Honey Salve
UV protection for head and muzzle: Absorbine Ultrashield Fly Mask and Mug Balm
For UV protection of the entire horse: PC Fly Sheet and Mug Balm
For UV protection and plant repellent: PC Fly Protection Boots

Find more insect and UV protection here.

Sources: Seges and Netdyredoktor