Acne Mechanica

The problem arises when heat, pressure, occlusion and friction combine over hair-bearing skin, obstructing the hair follicles and producing inflamed spots. Sweat and tight, non-breathable kit make it worse.

The clue to the diagnosis is the distribution, which follows the points where equipment or clothing contacts the skin. Helmets and headbands cause spots at the forehead and hairline, chin straps cause them along the jaw in sports such as American football, cricket and horse riding, and shoulder pads and backpack straps cause them across the shoulders and upper back. Tight or occlusive clothing, and cotton undergarments worn under kit, produce spots on the trunk and thighs. The eruption is usually made up of inflammatory papules and pustules in these contact areas, and can progress to deeper nodules if it persists. A telling feature is that it often improves markedly at the end of the season when the equipment is no longer worn, which points to the mechanical cause.

Several conditions resemble acne mechanica, and distinguishing them matters because the treatments differ. Ordinary acne, acne vulgaris, tends to affect the typical acne sites and includes blackheads and whiteheads, and it is driven by hormonal and other factors rather than by equipment; the two can coexist. The most important mimic is Malassezia folliculitis, also called pityrosporum folliculitis, a yeast infection of the hair follicles that produces itchy, uniform papules and pustules on the upper back, chest and shoulders, often worsened by sweating and occlusion. It looks like acne but does not respond to antibiotics, and can even be made worse by them, so a persistent, itchy, uniform eruption that fails acne treatment should prompt consideration of Malassezia folliculitis and treatment with an antifungal. The absence of blackheads and whiteheads is a useful clue, since Malassezia folliculitis lacks the comedones of ordinary acne, and a skin scraping or microscopy can confirm the diagnosis where it is uncertain, rather than assuming every itchy monomorphic eruption is fungal. Irritant or contact dermatitis from the chemicals used to clean equipment can also mimic the picture.

Recognising the mechanical pattern, and separating it from a yeast folliculitis in particular, avoids prolonged and ineffective antibiotic courses.

Management starts with reducing the mechanical trigger, and this is often enough on its own.

Wearing a clean, breathable, moisture-wicking and non-occlusive layer under equipment, using well-fitting and clean padding, showering and changing out of sweaty kit promptly, and avoiding greasy or occlusive skin products all reduce the heat, sweat and occlusion that drive the condition. On top of this, topical acne treatments help, including benzoyl peroxide, a topical retinoid such as adapalene, and salicylic acid. If antibiotics are used for inflammatory disease, follow standard acne prescribing: avoid antibiotic monotherapy, combine an antibiotic with a non-antibiotic topical such as benzoyl peroxide or a retinoid, and limit the duration, and reconsider the diagnosis if the eruption is actually a Malassezia folliculitis. Severe, nodular, scarring or treatment-resistant disease should be referred, as it may need specialist systemic treatment. Oral isotretinoin is reserved for severe, treatment-resistant or scarring acne under specialist care and current Medicines and Healthcare products Regulatory Agency (MHRA) safeguards, and for an athlete it is worth being aware of its recognised musculoskeletal effects, such as myalgia and arthralgia, which can be relevant to training and should be discussed.

• •Acne mechanica is driven by heat, pressure, occlusion and friction over sweaty skin.
• •Its distribution follows equipment and clothing contact points, and it eases when kit is not worn.
• •Reducing the mechanical and occlusive trigger is the central treatment.
• •Topical retinoids, benzoyl peroxide and salicylic acid help; if antibiotics are used, avoid monotherapy, combine with a non-antibiotic topical, and limit the duration.
• •Malassezia folliculitis mimics it but needs an antifungal, not antibiotics.
• •Refer severe, nodular or scarring disease; isotretinoin is specialist-only under MHRA safeguards and can cause myalgia and arthralgia.