• Diagnosis is usually made on the basis of clinical appearance.
• On the body:
• The rash typically presents as one or more red or pink, flat or slightly raised, patches of skin which enlarge to become ring-shaped lesions with red, scaly borders with a clear central area.
• However, more rarely, the lesions can appear as:
• Numerous overlapping concentric circles (tinea imbricate).
• Herpetiform subcorneal vesicles or pustules (bullous tinea corporis).
• In the groin:
• The most commonly affected areas are the inguinal folds and proximal medial thighs. The perianal skin and buttocks may be affected, but in men the penis and scrotum are often spared.
• The clinical presentation is variable, but the lesions are commonly red to red-brown, flat or slightly raised plaques with active borders (pustules or vesicles). They often itch, and in some cases there is uniform scale without central clearing.
• Fluorescence is not seen when the rash is examined with a Wood's light.
• Exclude other skin disease that look like a dermatophyte infection of the body or groin.

This recommendation is based on expert opinion [Weinstein and Berman, 2002; Hainer, 2003; Hay and Moore, 2004; Loo, 2004; Sarkany et al, 2004; Andrews and Burns, 2008; Havlickova and Friedrich, 2008].

Skin conditions which can look similar to fungal infection of the body

• Discoid eczema — plaques of papulo-vesicles tend to occur symmetrically on the limbs.
• Pityriasis rosea — symmetrical, and typically affects the trunk and the proximal limbs. The herald patch is almost impossible to differentiate from ringworm without microscopy of scales.
• Pityriasis versicolor — patchy, sharply demarcated macules, with fine scale. Usually there is less inflammation than with tinea corporis. Under Wood's light, the scaly lesions may show pale yellow fluorescence.
• Psoriasis — usually present on the knees, elbows, and scalp. Pitting of the nails may be present.
• Granuloma annulare — single or multiple rings of small, smooth, red or flesh-coloured papules. Itch may be present.

Skin conditions which can look similar to fungal infection of the groin

• Candidal intertrigo — usually more uniformly red, with no central clearing, and may have satellite lesions (see the CKS topic on Candida - skin).
• Erythrasma — more uniformly brown with slight scaling and no active border. Fluoresces a brilliant coral-red.
• Mechanical intertrigo — sharp edge, no central clearing or scale.
• Psoriasis — sharp margination, pitted nails, and knee, elbow, and scalp lesions.
• Seborrhoeic dermatitis — greasy scales, associated with scalp dandruff (see the CKS topic on Seborrhoeic dermatitis).

• Diagnostic tests are not usually required, but take samples for microscopy and culture if:
• The diagnosis is unclear.
• The infection has not responded to standard topical antifungals.
• Oral antifungal treatment is being considered.
• To take samples for fungal investigation:
• Wipe off any treatment creams before sampling.
• Scrape skin from the advancing edge of the lesion using a blunt scalpel blade or similar implement.
• Collect 5 mm² of skin flakes for microscopy and culture.
• Collect the sample into folded dark paper squares (secure with a paper clip), or use a commercially available fungal packet.
• Keep samples at room temperature. Do not refrigerate.
• Ensure clinical details are stated, including any treatment, animal contact, and overseas travel.
• Swabs are usually of no value for dermatophyte infections, but may provide a culture result if scrapings are inadequate.

When to take samples for microscopy and culture

• This recommendation is based on expert opinion [Weinstein and Berman, 2002; Hainer, 2003; Andrews and Burns, 2008; HPA, 2009].

How to take samples

• These recommendations are based on guidance from the Health Protection Agency [HPA, 2009].