What is folliculitis?
Folliculitis is the name given to a group of skin conditions in which there are inflamed hair follicles. The result is a tender red spot, often with a surface pustule.
Folliculitis may be superficial or deep. It can affect anywhere there are hairs, including chest, back, buttocks, arms and legs. Acne and its variants are also types of folliculitis.
What causes folliculitis?
Folliculitis can be due to infection, occlusion (blockage), irritation and various skin diseases.
Folliculitis due to infection
To determine if folliculitis is due to an infection, swabs should be taken from the pustules for cytology and culture in the laboratory.
Bacterial folliculitis is commonly due to Staphylococcus aureus. If the infection involves the deep part of the follicle, it results in a painful boil. Recommended treatment includes careful hygiene, antiseptic cleanser or cream, antibiotic ointment, and/or oral antibiotics.
Spa pool folliculitis is due to infection with Pseudomonas aeruginosa, which thrives in inadequately chlorinated warm water. Gram negative folliculitis is a pustular facial eruption also due to infection with Pseudomonas aeruginosa or other similar organisms. When it appears, it usually follows tetracycline treatment of acne, but is quite rare.
The most common yeast to cause a folliculitis is Pityrosporum ovale, also known as Malassezia. Malassezia folliculitis (Pityrosporum folliculitis) is an itchy acne-like condition usually affecting the upper trunk of a young adult. Treatment includes avoiding moisturisers, stopping any antibiotics and topical antifungal or oral antifungal medication for several weeks.
Ringworm of the scalp (tinea capitis) usually results in scaling and hair loss, but sometimes results in folliculitis. In New Zealand, cat ringworm (Microsporum canis) is the commonest organism causing scalp fungal infection. Other fungi such as Trichophyton tonsurans are increasingly reported. Treatment is with oral antifungal agents for several months.
Folliculitis may caused by herpes simplex virus. This tends to be tender, and resolves without treatment in around 10 days. Severe recurrent attacks may be treated with aciclovir and other antiviral agents.
Herpes zoster (the cause of shingles) may also present as folliculitis with painful pustules and crusted spots within a dermatome (an area of skin supplied by a single nerve). It is treated with hihg-dose aciclovir.
Folliculitis on the face or scalp of older or immunosuppressed adults may be due to colonisation by hair follicle mites (demodex). This is known as demodicosis.
The human infestation, scabies, often provokes folliculitis, as well as non-follicular papules, vesicles and pustules.
Folliculitis due to irritation from regrowing hairs
Folliculitis may arise as hairs regrow after shaving, waxing, electrolysis or plucking. Swabs taken from the pustules are sterile ie there is no growth of bacteria or other organisms. In the beard area irritant folliculitis is known as pseudofolliculitis barbae.
Irritant folliculitis is also common on the lower legs of women (shaving rash). It is frequently very itchy. Treatment is by stopping hair removal, and not beginning again for about three months after the folliculitis has settled. To prevent reoccurring irritant folliculitis, use a gentle hair removal method, such as a lady's electric razor. Avoid soap and apply plenty of shaving gel, if using a blade shaver.
Folliculitis due to contact reactions
Paraffin-based ointments, moisturisers, and adhesive plasters may all result in a sterile folliculitis. If a moisturiser is needed, choose an oil-free product, as it is less likely to cause occlusion.
Coal tar, cutting oils and other chemicals may cause an irritant folliculitis. Avoid contact with the causative product.
Overuse of topical steroids may produce a folliculitis. Perioral dermatitis is a facial folliculitis provoked by moisturisers and topical steroids. Perioral dermatitis is treated with tetracycline antibiotics for six weeks or so.
Folliculitis due to immunosuppression
Eosinophilic folliculitis is a specific type of folliculitis that may arise in some immune suppressed individuals such as those infected by human immunodeficiency virus (HIV) or those who have cancer.
Folliculitis due to drugs
Folliculitis may be due to drugs, particularly corticosteroids (steroid acne), androgens (male hormones), ACTH, lithium, isoniazid (INH), phenytoin and B-complex vitamins. Protein kinase inhibitors (epidermal growth factor receptor inhibitors) and targeted therapy for metastatic melanoma (vemurafenib, dabrafenib) nearly always result in folliculitis.
Folliculitis due to inflammatory skin diseases
Certain uncommon inflammatory skin diseases may cause permanent hair loss and scarring because of deep seated sterile folliculitis. These include:
Treatment depends on the underlying condition and its severity. A skin biopsy is often necessary to establish the diagnosis.
Acne and acne-like or acneiform disorders are also forms of folliculitis. These include:
The follicular occlusion syndrome refers to:
- Hidradenitis suppurativa (acne inversa)
- Acne conglobata (a severe form of nodulocystic acne)
- Dissecting cellulitis (perifolliculitis capitis abscedens et suffodiens)
- Pilonidal sinus.
Folliculitis affecting the buttocks is quite common and is often nonspecific, ie no specific cause is found. Buttock folliculitis is equally common in males and females.
- Acute buttock folliculitis is usually bacterial in origin (like boils), resulting in red painful papules and pustules. It clears with antibiotics.
- Chronic buttock folliculitis does not often cause significant symptoms but it can be very persistent. Although antiseptics, topical acne treatments, peeling agents such as alphahydroxy acids, long courses of oral antibiotics and isotretinoin can help buttock folliculitis, they are not always effective. Hair removal might be worth trying if the affected area is hairy. As regrowth of hair can make it worse, permanent hair reduction by laser or intense pulsed light (IPL) is best.
- Durdu M, Ilkit M. First step in the differential diagnosis of folliculitis: cytology. Crit Rev Microbiol. 2013 Feb;39(1):9-25. doi: 10.3109/1040841X.2012.682051. Epub 2012 May 29. Review. PubMed PMID: 22639852.
On DermNet NZ:
- Furunculosis (boils)
- Scalp folliculitis
- Oil folliculitis
- Gram negative folliculitis
- Spa pool folliculitis
- Pseudofolliculitis barbae (razor bumps)
- Pityrosporum folliculitis
- Folliculitis decalvans
- Patient information: folliculitis (the basics) – UpToDate (for subscribers)
- Folliculitis – Medscape Reference
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