Treatments for Photosensitization of the Lower Legs in Horses

Horses, though not originally native to the United States, are one of America's most prized animals. From the colonial period to modern day equestrian shows, horses are a staple in American culture. Photosensitization is a medical condition that can affect horses, especially in the lower leg.

  1. Photosensitization

    • Photosensitization is a medical condition in which areas of the skin become hypersensitive to sunlight causing lesions, sunburns and sores. This is a painful condition; horses with this condition are prone to skin infections due to the open sores. The skin in the lower leg is more exposed than other areas, like the back or neck regions, making it more susceptible to the sun's rays.

    Causes

    • There are two types of photosensitization: primary and secondary. Primary photosensitization occurs when a horse eats something with photo-activating properties. Certain grasses and grains can cause this condition. Secondary photosensitization occurs with the consumption of forage plants containing chlorophyll and a coinciding liver impingement. A liver impingement in a horse occurs when the bile ducts are blocked or advanced degradation occurs, limiting the liver's ability to process certain chemicals. After chlorophyll is processed in a horse, it is converted to a chemical called phylloerythrin, a photo-activating substance. If liver impingement is present, the phylloerythin cannot be excreted from the body, causing secondary photosensitization.

    Treatment: Foods to Avoid

    • For primary photosensitization, there are certain foods to avoid. St. Jon's Wart, buckwheat, burr trefoil and rye are known to cause this condition. Citrus fruits, clover, carrots, parsley and fennel are other plants that can cause this painful and debilitating condition. Avoid letting the horse consume these plants. Avoiding these foods is the primary treatment for this type of photosensitization.

    Treatments

    • Corticosteroids, if given in the early stages of the secondary version, can help lesson the condition. While the liver heals and the impingement remedies, keep the horse in shade. Because the lower legs are exceedingly sensitive, if possible, wrap the lower legs with ace bandages or strips of cotton fabric. This adds extra UV protection. If lesions have already formed, basic wound care is needed. Antibiotic ointments, pain management, and regular cleaning of the wound and bandage changing are vital treatments. The liver does regenerate itself; this allow for liver impingement to resolve itself with time, as long as liver damage is not too severe. A veterinarian can see the extent of damage. Refrain from feeding forage plants to the horse during impingement. This reduces the hypersensitivity of the skin.