Lice, ticks, and gnats are observed in folds, under the mane, and in the ears. Treatment with shampoos containing pyrethrin, permethrin, or other parasiticides provide effective treatment. Treatment is by excision and treatment with anti-parasitic drugs and ointments. These sores can appear anywhere on the horse's body, but commonly are found on the sheath and legs. Larvae of the Onchocerca species produce nodules on the chest and neck.
Skin tumors are one of the most frequent cancers from which horses suffer.
Squamous cell carcinomas often occur around the eyes or the sheath in light-skinned horses. This tumor usually is very malignant and spreads to surrounding tissues quickly. Surgical removal and local chemotherapy provide the best chance of cure. Sarcoids are thought to be viral in origin and often occur on the trunk and around the eyes. Surgical removal, local chemotherapy, and cryosurgery all have been used as treatments.