The skin is the largest organ in any animal. It protects the body from infection, injury and disease. However there are quite a few ailments horses can get that affect this organ.
External parasites:
These are parasites such as lice, leg mites, and pin worm. They are commonly seen in spring coming out of winter and can cause welfare issues and severely impact on a horses quality of life.
Mud fever:
Most commonly seen when the ground is wet (autumn/winter/spring). This is also known as pastern dermatitis and is often caused by bacteria. This is because the wet conditions cause the skin to soften and mud rubs against this softened skin causing damage to the surface where bacteria can enter. it is usually easily remedied by removing the horse from the wet surface. Drying the legs thoroughly and removing the scabs. Vet attention should be sought if there is any swelling, lameness or if the lesions are not resolving with treatment.
Ringworm:
Commonly seen on young horses or those who have an impaired immune system. It is actually a fungus and these lesions can be self resolving but are extremely contagious including in humans! It is important to get veterinary attention and ensure no sharing of tack, brushes or rugs whilst the infection is active.
Sarcoids:
Commonly seen in horses, ponies and donkeys. There are a variety of different types of lesions all of which need treated. These are a type of skin cancer that will spread through the skin but will not spread to other organs.
All of these issues need veterinary treatment.