• Look for typical features suggestive of scalp ringworm:
• Scalp scaling.
• Patchy, irregular hair loss.
• Lymphadenopathy (postauricular and cervical).
• Itch.
• In some people, a more severe inflammatory reaction can occur, causing:
• Erythema.
• Pustules.
• Crusting.
• Pustular boggy masses (kerion).
• Permanent alopecia and scarring of hair follicles.
• Itchy papules around the outer helix of the ear (a reactive phenomenon known as an id response).
• Wood's light examination is not routinely recommended to diagnose fungal scalp infections.
• Exclude other diagnoses:
• Seborrhoeic dermatitis — scaling of the scalp without significant hair loss. See the CKS topic on Seborrhoeic dermatitis.
• Alopecia areata — usually there is complete alopecia in the affected areas (rather than the patchy alopecia seen with scalp ringworm) with little or no scaling or inflammation. See the CKS topic on Alopecia areata.
• Traction alopecia — stress on the hair and hair shaft by tight braiding.
• Trichotillomania — obsessive compulsive disorder of pulling one's own hair. Hair within the lesion is of various lengths and there is little scalp involvement.
• Psoriasis — usually more scaling is present.
• Always carry out investigations to confirm the diagnosis.

These recommendations are based on a report on the diagnosis of scalp ringworm from the Health Protection Agency [HPA, 2007], an expert-consensus guideline on the management of scalp ringworm from the British Association of Dermatologists [Higgins et al, 2000], and expert opinion [Abdel-Rahman and Nahata, 1997; Andrews and Burns, 2008].

• Wood's light examination can be useful in identifying Microsporum canis and Microsporum audouinii because they will fluoresce blue-green [Andrews and Burns, 2008]. However, many of the organisms that cause scalp ringworm in the UK (including Trichophyton tonsurans) do not fluoresce under Wood's light [Higgins et al, 2000; González et al, 2007; HPA, 2007].

• Always use laboratory methods to confirm the diagnosis, unless a kerion (pustular boggy mass) is suspected, in which case the person should be referred immediately to dermatology.
• If there is clinical suspicion of scalp ringworm, scrape affected areas with a blunt scalpel blade or similar implement, to collect affected hairs, broken-off hair stubs, and scalp scale. Also pluck hairs from affected areas if possible (this may be difficult for children to tolerate).
• This method of sampling is not suitable for detecting carriers as they do not have any abnormal areas from which to take scrapings.
• If this is not possible, or the person is thought to be an asymptomatic carrier, brush with an unused toothbrush or cytobrush (the brush normally used to take cervical smears), passing the brush through the hair several times in the area of clinical abnormality (or in suspected carriers, different areas of the scalp), and then send the brush for culture.
• When taking samples, it is important to:
• Wipe off any treatment creams before sampling.
• Collect at least 5 mm² of skin flakes and hair.
• 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.
• Send samples for microscopy (results available within 24 hours) and culture (takes 2–3 weeks).

Confirming the diagnosis

• The recommendation that microscopy and culture should be used to confirm the diagnosis, and the advice on how to take samples is based on expert opinion from the Health Protection Agency [HPA, 2007; HPA, 2009].
• Microscopy of skin scrapings and hair shafts can confirm infection. However, false negatives are common even with experienced examiners. Fungal culture is more sensitive than microscopy, allows identification of the causative organism, and may guide treatment [Higgins et al, 2000; Andrews and Burns, 2008].

Using a cytobrush

• The recommendation to use a cytobrush is based on a prospective, observational, comparative study of 178 people. Of the people studied, mycologically proven tinea capitis was detected using skin scrapings in 115/135 (85.1%), compared with 132/135 (97.7%) with the cytobrush method (p = 0.025) [Bonifaz et al, 2007].