Alopecia or hair loss in horses can occur for several different reasons and may be temporary or permanent. [1] Alopecia refers to the partial or complete absence of hair that occurs in any area of the body where hair is normally present. [1][2]

Congenital alopecia is a condition that is present at the time of birth. [2] This form of alopecia is non-inflammatory and may occur due to genetic factors, resulting in damage to the hair follicles. [1][2]

Acquired alopecia refers to a partial or complete loss of hair that occurs at any stage of life. [2] It is the most common form of hair loss that affects horses. [2]

Successful treatment of hair loss requires identifying and addressing the underlying cause of the condition. [1] Diagnostic dermatology and blood tests can aid in the diagnosis of acquired alopecia.

Strategies to help prevent hair loss include evaluating your horse’s skin and hair regularly, providing balanced nutrition, and treating injuries and wounds promptly.

Hair Loss in Horses

Alopecia is known to occur in various species, including humans, horses, dogs, cats, cattle, and mice. [1] The condition describes the partial or complete lack of hair in areas where it is normally present. [1]

Types of Alopecia

Depending on the cause of the condition, alopecia is classified as congenital or acquired.

Congenital Alopecia

This form of alopecia is present at birth and occurs because of damage to the hair follicles that may be associated with genetic factors. [2]

Congenital alopecia may or may not be hereditary and does not occur in conjunction with signs of clinical inflammation. There is no treatment for congenital alopecia. [2]

Acquired Alopecia

More common in horses than congenital alopecia, acquired alopecia is not present at birth but can occur at any stage of life. [2] This form of alopecia is classified as either non-inflammatory or inflammatory.[2]

Horses with acquired alopecia are born with normal hair and healthy hair follicles that can produce normal hair. [2] However, acquired alopecia results in the loss of hair due to internal or external factors.

Non-inflammatory causes of acquired alopecia in horses include autoimmune disease, stress factors such as illness, seasonal changes, rubs due to poorly fitted blankets or equipment, nutritional deficiencies, and low thyroid hormones. [2]

Inflammatory causes of acquired alopecia include infections affecting the skin or hair follicles, trauma to the skin and hair follicles, such as burns, allergic skin reactions, and skin cancer. [2]

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Prevalence

The exact number of horses affected by alopecia is unknown.

A retrospective study by researchers at UC Davis determined the prevalence of alopecia areata in various equine breeds was 0.017%. [3]

This study found that Appaloosas and Quarter Horse breeds were most commonly affected by the condition. [3]

Areas on the body where hair loss was most likely to occur included the mane, tail, and face of the horses. [3] The median age of affected horses was nine years, and the condition affected horses ranged from 3 to 15 years.

More than half of the horses presenting with alopecia had other medical conditions. [3] Five of seven (71.4%) owners reported a seasonal occurrence of alopecia in their horses and a worsening of the condition in the spring and summer. [3]

Clinical Signs

The clinical signs of alopecia depend on the type of and underlying cause of the condition.

Signs of congenital alopecia typically include: [2]

  • Symmetric hair loss
  • Hair loss that is localized to one area of the body
  • Well-demarcated areas of hair loss

Signs of acquired alopecia may include: [4]

  • Variation in patterns of hair loss depending on the underlying cause of the condition
  • Hair loss that is diffuse or localized to one area
  • Hair loss that is symmetric or asymmetric
  • Hyperpigmentation of hairs
  • Swelling, scaling, shedding, itching (pruritus), and thickened skin (lichenification) if inflammation is present
  • Secondary skin diseases such as bacterial infections
  • Secondary skin conditions including oily secretions of the sebaceous glands (seborrhea)

Causes

Congenital Alopecia

Congenital alopecia is rare in horses. The condition may or may not be hereditary. It results from abnormalities in the development and or function of hair follicles such as: [1][5]

  • Reduced quality and quantity of hair follicles, including follicles that do not develop completely (hair follicle aplasia) or develop abnormally (hair follicle dysplasia)
  • Reduced quality and quantity of hair fibers produced by the hair follicles

There is only one scientifically documented case of congenital alopecia occurring in a horse that was born with partial alopecia. By the time the blue roan Percheron was one year of age, the condition had progressed to become body-wide alopecia. [6]

Studies in humans and other animals suggest congenital alopecia is a complex trait involving many genes. [16]

Acquired Alopecia Associated with Inflammation

When acquired alopecia involves inflammation, inflammatory cells are present in the area where hair loss is occurring. Inflammation may result from: [1]

  • Bacterial infection
  • Fungal infection (such as ringworm infection known as dermatophytosis) [2][7]
  • Parasitic infection (associated with organisms such as ticks, fleas, demodex mites, or roundworms known as onchocercia)
  • Trauma to the skin (such as burns and injury)
  • Allergies (skin irritation, allergic reaction to specific foods, insect hypersensitivity)
  • Cancer [2][8]
  • Severe diseases involving skin infection and inflammation (cellulitis)
  • Infection of the hair follicles (folliculitis)

The above-mentioned conditions may lead to hair loss on their own but may involve itching (pruritis) that further contributes to hair loss. [1][9] Pruritis can cause affected horses to rub irritated and or painful areas of skin, thus promoting hair loss. [1]

Acquired Alopecia that is Non-Inflammatory

Acquired alopecia that is non-inflammatory (no clinical signs of inflammation) is caused by factors that slow or inhibit the growth of hair follicles, such as: [1][2][10]

  • Nutritional deficiencies (particularly protein)
  • Hormonal imbalances (such as low thyroid hormones or high estrogen level)
  • Pregnancy or lactation
  • Illness and fever
  • Autoimmune disease (alopecia areata, which involves diffuse hair loss, and linear alopecia which involves vertically linear areas of hair loss are conditions in which the immune system attacks the hair follicles.)
  • Changes in season (reported cases of seasonal alopecia that occur in the spring and summer)
  • Poisoning from mercury, thallium, and iodine
  • Friction due to poorly fitting blankets or equipment
  • Trauma to hair shafts due to excessive grooming, prolonged exposure to UV light, or exposure to chemical trauma from shampoos, pesticides, alcohol, and solvents
  • Stressors such as high fever, severe illness, pregnancy, surgery, anesthesia, and metabolic disease

Anagen effluvium refers to the abnormal diffuse loss of hair during the growth phase of the hair cycle.

Telogen effluvium refers to the abnormal diffuse hair loss during the resting phase of the hair cycle.

Diffuse hair loss is commonly due to telogen or anagen effluvium that is non-scarring and not associated with inflammation. Anagen effluvium and telogen effluvium are caused by an event such as (fever, metabolic disease, or infectious disease) that disrupts that hair follicle. [1]

In some occurrences of alopecia in horses, the causes of the condition are unknown (idiopathic).

Diagnosis

Your veterinarian can provide a diagnosis of alopecia and identify the underlying cause of the condition. Determining whether alopecia is inflammatory or noninflammatory is critical to selecting an appropriate treatment. [1]

To diagnose alopecia, your veterinarian will consider your horse’s prior medical history and any predisposition to congenital or hereditary alopecia. Your veterinarian may also use one or more of the following strategies to diagnose alopecia: [1][2]

Physical Examination

During a physical examination, your veterinarian will note: [1]

  • Pattern and distribution of hair loss
  • Length of time alopecia has been present
  • If hairs are being shed or are breaking off
  • Signs of secondary skin infections
  • Presence of parasites or fungus on the skin and or hair
  • Presence or absence of itching, reddened skin, or rash

Laboratory Testing

Diagnostic tests for alopecia may include skin scrapings, smears, biopsies or blood tests. [1]

Skin Scrapings

A scraping of the skin and hair may be collected to determine if parasites such as fleas, mites, and lice (ectoparasites) are present on the hair or skin. Samples of the skin and hair are assessed under a microscope.

Skin Smear

A sample referred to as a smear may be collected from the skin and examined under a microscope to check for evidence of bacterial, fungal, or yeast infections.

Skin Biopsies

Skin biopsies may be taken to confirm if cancer or bacterial or parasitic infections are the underlying cause of alopecia. Biopsies may be collected from the areas of skin on the body where alopecia is occurring and on unaffected areas for comparison purposes.

A skin biopsy can help your veterinarian determine if alopecia is associated with inflammation or not. It can also provide information on the structure and number of hair follicles and the ratio between follicles that are not actively growing hair (in a state of dormancy) and those that are producing hair.

Blood Tests

If your veterinarian suspects your horse may have an endocrine issue such as low thyroid hormones or high estrogen level, blood samples may be collected to assess hormone levels.

Treatment

Alopecia may resolve once any underlying condition causing it is identified and treated. Treatment strategies applicable for horses with hair loss may include medication, nutritional management and supportive care.

In some horses affected by alopecia, hair may regrow on its own if hair follicles are healthy. New hair can grow from a dormant follicle that becomes active again.

In cases where follicles have been affected by illness or nutritional deficiency, regrowth may occur once the horse’s health status improves. Once a hair follicle is destroyed, it cannot grow another hair.

Medication

Antibiotics:

Various classes of antibiotics target specific types of pathogenic bacteria and may be used to treat diverse infections, including those resulting in alopecia. Veterinary advice is critical for determining when antibiotics are necessary.

Antibiotics commonly used for treating infections in horses include sulfadiazine, trimethoprim, sulfamethoxazole, penicillin, gentamicin, enrofloxacin, and ceftiofur. [11]

Topical Antifungals:

In cases of alopecia caused by a fungal infection of the hair shaft (a condition known as Piedra), a topical antifungal my be applied. [2]

Oral Corticosteroids:

Steroids may be prescribed to help control itching and inflammation associated with alopecia. Anecdotal reports describe the successful use of corticosteroids, such as prednisolone, for stimulating hair growth in cases of alopecia areata. [2]

Topical Drugs:

According to case reports, topical applications of medications, including minoxidil (a vasodilator) and tacrolimus (an immunosuppressant), can successfully stimulate hair growth in some horses with alopecia. [2]

Topical antimicrobial medications may be used to treat bacterial or yeast infections that may be contributing to alopecia. [2]

Thyroid Hormone Replacement:

Oral L-triiodothyronine (a thyroid hormone) has been reportedly used in cases of equine alopecia to promote hair growth by correcting low thyroid hormone levels. [2]

Parasite Control:

Parasite control using insecticide medications may be prescribed to treat alopecia associated with parasite infestation (with fleas, ticks, or mites) and itching due to the infection. [12]

Nutritional Management

Hair growth requires adequate nutrition in your horse’s diet, including sufficient protein, vitamins and minerals.

The best way to meet your horse’s nutritional requirements is to feed a balanced forage-based diet with adequate vitamin and mineral supplementation. Ensure that your horse’s diet provides enough of the following key nutrients:

Amino Acids:

Your horse’s hair coat is mainly comprised of the protein keratin, made up of amino acids including methionine and cysteine. Ensure your horse gets adequate sulfur-containing amino acids in their diet to support the growth of strong, healthy hair.

Essential Fatty Acids:

Omega-3 fatty acids improve skin barrier function, helping to seal in moisture and protect against irritants that could affect coat and skin conditions. [13]

Biotin:

A B-complex vitamin, biotin is important for skin health and hair growth. Biotin is required for the production of keratin, a structural protein found in hair and skin tissue. Severe biotin deficiency can cause alopecia. [15]

Vitamin E:

Vitamin E is a fat-soluble vitamin that acts as an important antioxidant for horses. It helps to support healthy skin by protecting skin cells from oxidative damage. [14]

Vitamin A:

Vitamin A (retinol, retinoic acid) is another fat-soluble vitamin that plays a role in skin and hair coat quality in horses. A deficiency in Vitamin A can lead to dry skin, dull coats, and brittle hair.

The best way to meet your horse’s vitamin and mineral needs is to feed a comprehensive nutritional supplement, such as Mad Barn’s Omneity. An all-in-one supplement, Omneity provides all of the vitamins and minerals required to support your horse’s overall well-being and to grow out a shiny, healthy coat.

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Untreatable Alopecia

Scarring alopecia (also referred to as cicatrichial alopecia) involves permanent destruction of the hair follicles. [2] Hair regrowth does not occur in cases of scarring alopecia caused by: [2]

  • Thermal, physical, or chemical injury
  • Abnormal and excessive growth of tissue (tumor)
  • Severe infection of the hair follicles
  • Parasitic skin infection with the worm Onchocerca volvulus (a condition referred to as cutaneous onchocerciasis) [2]

Congenital Alopecia

Currently, there are no scientifically reported treatments available for congenital alopecia.

Prevention

There is no known way to prevent congenital alopecia. Some types of acquired alopecia may be preventable.

Consider the following strategies to help prevent certain types of acquired hair loss in horses:

Provide Timely Veterinary Care

If your horse is showing signs of itching or infection, consult with a veterinarian promptly to determine a diagnosis and appropriate treatment. Infections left untreated may worsen and increase the risk of hair loss among other health problems.

Use Proper Fitting Blankets and Equipment

Avoiding using blankets and equipment that doesn’t fit properly to prevent hair loss due to rubs.

Assess Your Horse’s Skin Health

Check your horse’s skin and coat health regularly to identify any signs of injury, infection, and inflammation that may require treatment to avoid hair loss or other complications.

Follow our Daily Grooming Guide to keep your horse looking their best.

Consult with an Equine Nutritionist

Work with a nutritionist to ensure your horse’s diet is balanced and provides all essential nutrients required to support healthy coat growth. Feeding a balanced diet will prevent vitamin and mineral deficiencies that could cause hair loss.

Summary

  • Alopecia is either congenital or acquired.
  • Acquired alopecia is classified as inflammatory or non-inflammatory.
  • Acquired alopecia due to an inflammatory cause is the most common type of alopecia that occurs in horses.
  • Some forms of alopecia are treatable, whereas others are not.
  • Determining an appropriate treatment for alopecia requires identifying any underlying cause of the condition.
  • A veterinarian can diagnose alopecia based on a physical examination, skin scraping, skin biopsy, and laboratory testing.

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References

  1. Moriello, K. Alopecia in Animals. Merck Veterinary Manual. 2022.
  2. Rosychuk, RA. Noninflammatory, nonpruritic alopecia of horses. Vet Clin North Am Equine Pract. 2013. View Summary
  3. Hoolahan, DE et al. Equine alopecia areata: a retrospective clinical descriptive study at the University of California, Davis (1980-2011). Vet Dermatol. 2013. View Summary
  4. Wobeser, BK. Skin Diseases in Horses. Vet Clin North Am Equine Pract. 2015. View Summary
  5. Mecklenburg L. An overview on congenital alopecia in domestic animals. Vet Dermatol. 2006.
  6. Valentine BA, Hedstrom OR, Miller WH Jr, Scott DW, Mathies S. Congenital hypotrichosis in a Percheron draught horse. Vet Dermatol. 2001. View Summary
  7. Padalino B. et al. Rare Generalized Form of Fungal Dermatitis in a Horse: Case Report. Animals (Basel). 2020. View Summary
  8. Finley, MR. et al. Paraneoplastic pruritus and alopecia in a horse with diffuse lymphoma. J Am Vet Med Assoc. 1998. View Summary
  9. Moriello, K.A. Itching (Pruritus in Horses). Merck Veterinary Manual. Accessed 03/09/23.
  10. Stanley, O. and Hillidge, CJ. Alopecia associated with hypothyroidism in a horse. Equine Vet J. 1982. View Summary
  11. Antibiotics in Veterinary Medicine. University of Minnesota. Accessed 03/14/23.
  12. French, D. et al. External Parasite and Vector Control Guidelines. American Association of Equine Practitioners. 2016.
  13. Goh, YM. et al. Plasma n-3 and n-6 fatty acid profiles and their correlations to hair coat scores in horses kept under Malaysian conditions. J Vet Malaysia. 2004.
  14. Finno CJ, Valberg SJ. A comparative review of vitamin E and associated equine disorders. J Vet Intern Med. 2012. View Summary
  15. Whitehead, CC. Assessment of biotin deficiency in animals. Ann N Y Acad Sci. 1985.
  16. Alzolibani, A.A. Epidemiologic and genetic characteristics of alopecia areata (part 1) Acta Dermatoven. 2011.