SKIN INFECTIONS

May be bacterial, fungal, viral – common examples are listed below – or parasitic (lice, scabies) See also Parasites

Boil/carbuncle Abscess of a hair follicle/group of hair follicles, usually caused by Staph. aureus. Can scar if left to resolve without intervention

Cellulitis Bacterial infection (usually streptococcal or staphylococcal) of the skin, which becomes hot, red, painful, tender and swollen. Occurs most often on the legs, but possible in any area of the body, infection usually entering via a break in the skin. Fever, rigors and nausea may be present.

Cold sore (herpes simplex) Localised collection of blisters with a red base, usually on or around the lips, that develop into crusts and disappear without scarring. Manifestation of a recurring infection with the herpes simplex virus (HSV). Lesions are contagious until dried out

Folliculitis Inflammation of hair follicles, caused by infection (usually by Staph. aureus), friction or chemical irritation. Presents as a crop of small, rounded, yellow-red spots (pustules) on hair-bearing skin, eg, legs, shaved beard area in men

Fungal nail infection (onychomycosis) can involve the entire nail unit or any part of it. Four times more common in toenails than finger nails. As the infection develops, the nail unit discolours, the nail plate distorts, and the nail bed and adjacent tissue may thicken.

Groin infection (tinea cruris, ‘jock itch’)

Superficial fungal infection of the groin and surrounding skin. An often bilateral brownish-red scaling rash on the medial thigh and inguinal area, with pustules and vesicles at the borders. Causes burning and pruritus. May spread from groin to lower abdomen and buttocks. Generally seen in young men and obese adult males, common in athletes.

Impetigo

Highly contagious superficial bacterial infection (usually Staph. aureus and/or Strep. Pyogenes). Thin-walled blisters leave areas of exudation and yellowish crusting. Clusters of lesions develop, usually on the face, especially around the nose and mouth.

Intertrigo

Erythematous eruption in a skin fold (under the breasts, in the groin), where warmth, moisture and chafing predispose to opportunistic infection of the inflamed skin with Candida albicans although other Candida species may be involved. Often an incidental finding, or may present with itch or skin changes. Usually managed with topical antifungal preparations along with correction of predisposing factors, e.g. obesity. 

Molluscum contagiosum

Viral infection causing groups of smooth, pearly pink papules on face, trunk and neck, with characteristic central punctum. Clears spontaneously without scarring.

Ringworm (tinea corporis)

Superficial infection of skin by a dermatophyte fungus. Presents on trunk or limbs as one or many small, red, circular inflamed patches, with scaly edge and spreading outwards, often causing irritation. Lesions enlarge slowly and clear centrally. Scalp ringworm (tinea capitis) presents as scaly patches with areas of hair loss or broken hairs. May result in permanent alopecia and scarring. Occurs almost exclusively in prepubertal children, more common in black communities. Take skin scrapings and hair samples to confirm presence of fungal hyphae.

Warts

Rounded, elevated hyperkeratotic lesions that occur when the human papilloma virus (HPV) causes overgrowth of cells at the base of the epidermis. Can occur anywhere but commonly where skin is damaged, eg, on backs of hands, on fingers where there is nail biting, on shaved beard area in men. Vary in shape and size (1mm–1cm). The normal tiny lines of the skin do not cross the surface of a wart. Small black dots (capillaries) occasionally present. Warts are often classified by how they look.

• ‘Common’ warts: a flesh-coloured pimple becomes, over weeks, a rough, raised lump
• Plane (flat-topped, slightly raised), filiform (finger-like), mosaic (clustered)
• Plantar warts (verrucae) See Foot problems
• Seborrhoeic warts: common in older people; benign, appear as dark brown/ black spots almost stuck on the skin

See also Melanoma

SKIN AND NAIL SCRAPINGS

Used in the diagnosis of fungal skin and nail infections. A PHE guide (below) has tips on when and how to take scrapings

SKIN TAGS

Small, skin-coloured, pedunculated lesions; common and benign.

SLAPPED CHEEK SYNDROME (erythema infectiosum, fifth disease)

Viral infection (parvovirus B19) that may be asymptomatic but often presents with mild fever, sore throat and gastrointestinal upset; a bright erythematous rash (resembling slapped cheeks) may develop on the face, and may spread over the body, lasting 1-3 weeks. Usually affects school-aged children. In pregnancy, there are associated dangers.