Folliculitis in Dogs and Cats

Summary

Folliculitis is a term that refers to the inflammation of one or more hair follicles. In veterinary medicine, it’s most commonly discussed as bacterial folliculitis, a condition which involves the infection of hair follicles with bacteria and is widely considered the most common kind of canine skin infection.

The bacteria that infects the hair follicles of pets who suffer this condition typically resides on the surface of normal dog and cat skin. As such, bacterial folliculitis tends to occur when a healthy hair follicle is compromised, either by an underlying systemic disease, local trauma, or a specific disorder of the skin.

Systemic diseases that can lead to bacterial folliculitis include endocrine disorders (such as hypothyroidism and Cushing’s disease in dogs) and disorders of the immune system.

Skin disorders causing bacterial folliculitis in dogs include: canine acne, acral lick granuloma, skin fold pyoderma, interdigital pododermatitis (interdigital cysts), idiopathic furunculosis of German Shepherd Dogs, pyotraumatic folliculitis, and callus dermatitis, among others. In both dogs and cats, allergic skin disease is perhaps the most common cause of bacterial folliculitis. Parasitism and fungal infection of the skin are also common causes.

Symptoms and Identification

Regardless of the cause, the upshot of bacterial folliculitis is the same. Swelling, redness, itching, pustules (pimples) and hair loss are the most common symptoms, but the following may also be in evidence:

•  Papules (reddish swellings on the skin)

• Hyperpigmentation (darkening of the skin)

• Epidermal collarettes (circular areas of hair loss with crusting or scaling around their borders)

• Superficial erosions

• Draining tracts

• Pain around the affected areas

The diagnosis of bacterial folliculitis is typically made upon visual inspection and often after undertaking one or more of the following diagnostic tests:

•  Skin scrapings for mites

• Skin cytology

• Fungal culture

• Wood's lamp examination for fungus (ringworm)

• Bacterial culture and sensitivity

• Skin biopsy and histopathology

Affected Breeds

No breed predisposition has been specifically identified for bacterial folliculitis in general. Certain conditions predisposing pets to bacterial folliculitis (such as allergic skin disease), however, are considered hereditary and are therefore more prevalent in certain breeds.

Treatment

Treatment of bacterial folliculitis requires a three-pronged approach: topical therapy, systemic therapy, and treatment of any underlying disorder. Antimicrobial drugs are almost always employed.

Topical therapy most often involves the use of antimicrobial shampoos, whereas systemic therapy usually includes oral antibiotic medications. In the case of bacterial folliculitis, long-term use of both topical and systemic antimicrobials is typically required (three to twelve weeks).

Treatment of underlying conditions is highly specific to the individual disorder.

Veterinary Cost

Due to the relative ease of diagnosis in most cases, the initial costs involved in diagnosing bacterial folliculitis –– often less than $100-$200 –– are typically considered affordable. In complicated cases for which hard-to-diagnose underlying diseases are a possibility, however, diagnostic costs can climb to $500 - $1,000 or more, especially if systemic diseases are in play.

Despite the relatively low cost of diagnosis, treatment may prove expensive for many pets with bacterial folliculitis. That’s because of the long term nature of the typical treatment protocol and the high price of some of the antibiotics and topical agents required to treat these infections. In large dogs, for example, antibiotic therapy can easily cost many hundreds of dollars. What’s more, treatment of any underlying conditions may also prove expensive.

Prevention

The possibility of preventing bacterial folliculitis depends on whether or not its underlying cause can be prevented. For example, pets with flea allergy as an underlying cause are often highly manageable via strict flea prevention. Otherwise, this condition isn’t generally considered preventable.

References

Curtis CF, Bond R, Blunden AS, Thomson DG, McNeil PE, Whitbread TW. Canine eosinophilic folliculitis and furunculosis in three cases. J Small Anim Pract. 1995 Mar;36(3):119-23.

Fraser M. What is your diagnosis? Eosinophilic folliculitis and furunculosis. J Small Anim Pract. 2002 Apr;43(4):150, 187.

Mason IS, Mason KV, Lloyd DH. A review of the biology of canine skin with respect to the commensals Staphylococcus intermedius, Demodex canis and Malassezia pachydermatis. Vet Dermatol. 1996;7:119–132.

Sasaki A, Shimizu A, Kawano J, et al. Characteristics of Staphylococcus intermedius isolates from diseased and healthy dogs. J Vet Med Sci. 2005;67:103–106.

White SD, Brown AE, Chapman PL, et al.. Evaluation of aerobic bacteriologic culture of epidermal collarette specimens in dogs with superficial pyoderma. J Am Vet Med Assoc. 2005;226:904–908.