Most often seen in black patients; lesions are typically localised to the posterior neck. They begin as papules and pustules and may progress to confluent keloids. [24]

Possible aetiologies to consider include oral medicines, topical corticosteroids, contrast dye, testosterone, and cosmetic products.

Clinical clues include the abrupt onset of lesions within days of exposure, widespread involvement, atypical locations, atypical age, and improvement with cessation of medicine or exposure.

Comedones, pustules, and cysts are most commonly found behind the ears and in the axillae and groin.

Consider exposure to halogenated aromatic hydrocarbons (e.g., chlorinated dioxins and dibenzofurans). Patient may have systemic complications such as ophthalmic, neuropathic, hepatic, and lipoprotein abnormalities. [25]

Multiple open and closed comedones on the peri-orbital and malar areas, usually on older people with significant chronic sun exposure. Typically non-inflammatory.

Common condition that manifests as erythematous papules and pustules, which are follicularly based.

As opposed to acne, folliculitis often affects the trunk and extremities.

Occurs in patients with acne treated with long-term antibiotics who subsequently develop pustules or nodules on the anterior nares, which then spreads. Can also occur in people after hot tub immersion, as well as in HIV patients.

Firm yellowish-brown or red smooth papules peri-orbitally and characteristically on the eyelid skin. [27]

White keratinaceous cysts that are found on the face, particularly on the eyelids. Lesions are fixed and persistent.

Common peri-oral eruption of papules and pustules on an erythematous and/or scaling base, often the result of topical corticosteroid use. Localised symmetrically around the mouth, with a clear zone around the vermilion border. [28]

Rapid onset of reddish or cyanotic erythema with abscesses, cysts, and occasionally sinus tracts. No comedones and no involvement of back or chest. [29]

Typically affects older people than acne vulgaris, most often women aged 30 to 50 years.

Various forms, but classically presents with background erythema and telangiectasias, and inflammatory papules and pustules occasionally superimposed.

Environmental factors often act as triggers.

Non-inflammatory small papules that occur primarily on the eyelids and upper cheeks, usually multiple.

Disproportionately more prevalent in Japanese women.