Common Skin Infections

Folliculitis and Boils

Folliculitis, by definition, is an inflammation centered around and of the hair follicle. Clinically one sees folliculocentric itchy or tender papulopustules, often with a central hair protruding from them. Superficial infection - usually staphylococcus aureus - produces the clinical appearance of folliculitis, whereas more deep seated infection results in boils or carbuncles (large boils).

Folliculitis - note visible hair emerging from folliculocentric pustule

Pseudofolliculitis is the term used for a folliculitis due to ingrowing hairs rather than true primary bacterial infection (e.g. shaving rash of beard area or shaved/waxed legs). The main problem here is inflammation due to the irritation of the hairs rather than primary bacterial infection. However the two conditions overlap in practice. "Sycosis barbae" is yet another term - implying an infected shaving rash, but again hair irritation plays a role as well. Advising the patient to leave a small length of beard and to use clippers rather than an electric razor may help. I sometime suggest topical anti fungal/weak steroid combination once week after shaving to help keep it at bay.

Sycosis barbae-commoner in skin type 6

There are lots of causes of folliculitis and indeed the cause may be multi-factorial - infection, shaving practices, racial (genetic) variation, climate/humidity, occlusive clothes, occlusive medical dressings, use of very greasy moisturisers, rich ointments or hair pomades.

There are a number of specific 'folliculitis' entities which are worth knowing about - some more common than others.

1. Hot-tub folliculitis -Unhygienic jacuzzis can be a source of infection which is due to pseudomonas. This often spontaneously resolves but can be treated with topical antibiotic if needed.

'Hot-tub'pseudomonas folliculitis. Note cut off at waist with lesions only in immersed areas.

2. Pityrosporum folliculitis on trunk (see below in 'fungal' section). Note very monomorphic lesions.

Pityrosporum folliculits. Often seen in athletes or those who work in hot, sweaty environments

3. "Steroid acne" is a folliculitis secondary to systemic steroids (it is not a true acne but rather is an acneiform eruption).

Steroid acne- associated with use of oral steroids. Note how monomorphic the lesions are in this typical location for this diagnosis.

4. "Itchy folliculitis" is a very itchy folliculocentric eruption seen on the upper trunk and limbs, secondary to HIV infection (cause unknown). It has many eosinophils histologically and usually responds to Tetracyclines, but it is important to know about it as it can be a presenting sign of HIV infection. It has sometimes been called 'eosinophilic folliculitis'.

5. Folliculitis (or acne) keloidalis – This is very common in young black adult males. It is a 'folliculitis' on the nape of neck and occipital scalp which can progress to hypertrophic scars or keloid with hair loss. Occasionally the condition is very severe with deeper infection – the whole occipital scalp is boggy and discharging with scarring alopecia (called "dissecting cellulitis of scalp" or "perifolliculitis capitis"). Treatment is very difficult. Try avoiding shaving and long-term (more than 6 months) oral antibiotics. For severe cases triamcinolone injection into the scarred area or radical surgery is indicated. It is not really a true folliculitis in the bacterial sense but is included here for completeness.

Treatment of folliculitis:

"Infective form" is with topical antiseptics, topical antibiotics (e.g. fusidic acid) or oral antibiotics (e.g. flucloxacillin 500mg or erythromycin 500mg both four times daily for 2-4 weeks or longer). Remember to think about itchy folliculitis in widespread chest folliculitis and whether any element of occlusion with grease or ointments is provoking the problem. Advise patients to avoid tight clothes, occlusive dressings, use lighter moisturisers, and to rub moisturisers in the direction of hair growth etc.

"In-growing hair form" - avoid shaving if possible or shave less closely, without stretching the skin. I often use a weak hydrocortisone-fungal combination after shaving as a precautionary measure and many patients find this helpful.