Hair loss (also known as alopecia) in horses occurs for three main reasons: because the hair has been broken or rubbed off; the immune system is not working properly and an infection has taken root; or the immune system targets the hair as a foreign invader.
• Among many possible underlying causes, two common conditions which result in hair loss are dermatophytosis (also known as ringworm) and dermatophilosis (also known as rain rot, rain scald, or dew poisoning)
• Horses with patchy coats or bald spots require prompt veterinary attention to determine the underlying cause
• Diagnostic tools include physical examination, skin scrapes, hair plucks, cultures, and biopsies
• Treatment depends on diagnosis and range from improved hygienic practices to antibiotics, anti-inflammatories, and deworming medications
A closer look: Hair Loss (Alopecia) in Horses
Hair loss is common in horses, and is a symptom of a wide variety of possible underlying causes. Causes range in severity from mild and easily treatable to serious conditions requiring extensive treatment. Horses with a patchy coat or bald spots require prompt veterinary attention in order to determine the cause and plan treatment.
Possible causes
The potential causes of hair loss typically relate to several basic issues.
In some cases, the horse is rubbing the hair off, usually due to something that is causing itchiness. Potential conditions include:
- Biting insects and related allergies
- Parasitic infections, including mange
- Contact allergies
In some cases, the immune system is either overactive and sees the hair as a threat, or is underactive and allows an infection to take hold and kill the hair.
Other possible causes include
- Nutritional deficiencies
- Hormonal imbalances, especially during pregnancy and lactation
- Side effect from drugs
- Side effect during recovery from an illness
- Normal shedding during spring
- Ingestion of toxic materials, such as selenium
- Urine scalding
Risk factors
The main variation in severity of hair loss is the size and number of affected areas. Horses that have widespread, large patches of hair loss are more likely to have an immune-mediated disease such as an allergic reaction, whereas localized, multiple areas of hair loss are typically associated with infectious agents.
Hair loss also varies in whether the patches of missing hair are itchy. Horses that are itchy may self-mutilate or rub the itchy areas on objects, causing damage to the skin. Itchy hair loss is most commonly associated with infectious agents such as fungi or bacteria.
Testing and diagnosis
Horses with patchy coats or bald spots require prompt veterinary attention. Diagnostic tools include:
- Physical examination
- Hair plucks
- Skin scrapes
- Fungal cultures
- Blood work
- Urinalysis
- Skin biopsy
Treatment depends on underlying causes, and may include:
- Antibiotics for bacterial infections
- Anti-inflammatories for inflammation
- Deworming for parasitic infections
- Antifungals for fungal infections
- Corticosteroids or other immunosuppressive agents for allergic responses
- Increased hygiene practices, including bathing with medicated shampoos
- Increased insect management
- Cryosurgery
Similar symptoms
In some cases, a patchy coat is a result of seasonal shedding. During seasonal shedding, no areas of skin are hairless, but instead have a thinner layer of hair. Horses with truly hairless skin require examination by a veterinarian.