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Common superficial fungal infections of the skin

Rebecca Penzer
RGN BSc PGDip MSc
Opal Skin Solutions Independent Nurse Consultant in Skin Health
Oxford
E:rpenzer@ opalskin.co.uk

As Figure 1 shows, superficial fungal infections can be divided into two groups - dermatophyte and yeast infections.

[[NIP23_fig1_31]]

Dermatophyte (or ringworm) fungal infections are classified by associating the Latin word for the part of the body that they refer to with the word "tinea" (Latin for worm); thus, tinea capitis (ringworm of the scalp) and tinea corporis (ringworm of the body). There are three groups of fungal organisms involved in producing dermatophyte fungal infections - Trichophyton, Microsporum and Epidermophyton. Fungal organisms can also be distinguished by their preference for "living on" human bodies only (anthropophilic) or living on animals (zoophilic). Zoophilic organisms will also live on humans: for example, tinea corporis can be caught from animals. Zoophilic organisms also tend to cause more severe inflammatory responses in humans than anthropophilic organisms.
Yeast infections are generally caused by commensal organisms (organisms that live on different species in an intimate, nonparasitic relationship) that have become pathogenic. Reasons for this include immunosuppression, taking a course of antibiotics or the oral contraceptive pill. A common example is candidiasis.
All fungal infections, whether dermatophyte or yeast, live in the upper most keratin layer of the skin, the nail or the hair shaft.

Dermatophyte fungal infections

Tinea capitis
Scalp ringworm is usually seen in preadolescent children and for unknown reasons seems to occur most frequently in Afro-Caribbean children.(1) In the UK Trichophyton tonsurans has been identified as the usual infective agent.(1,2) This anthropophilic organism is transmitted by human-to-human contact. Microsporum canis, which used to be the most common cause of tinea capitis in the UK, is a zoophilic organism and is transmitted by contact with an infected kitten or puppy.
The key symptoms of tinea capitis are scalp hair loss and scaling. The fungal organism can damage the hair in two ways, which explains why the condition can look different in different individuals. Either it can penetrate the hair shaft (endothrix infection) or it can penetrate the hair shaft and grow over the outside of the hair shaft at the same time (exothrix infection). In an endothrix infection the hair breaks as it emerges from the scalp. Sometimes, where there is swelling of the hair follicle, little black dots can be seen on the scalp surface. T tonsurans causes this type of reaction. In exothrix infection the hair breaks part way down the hair shaft, leaving broken hairs as the key symptom. M canis affects the hair in this way. It is worth noting that historically a Wood's light has been a common way to diagnose tinea capitis. When M canis is the infecting agent, the Wood's light will cause green fluorescence of the fungal spores on the outside of the hair shaft - this method of diagnosis is effective only in exothrix infections when the spores cover the outside of the hair shaft. As most infections are now endothrix, this method is less useful and diagnosis must rely on mycological examination of the hair and scalp scale (see Box 1).

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In very serious inflammatory cases of tinea capitis (usually caused by a zoophilic organism), kerion can appear. These are purulent patches with a crust that when lifted reveals a damp, "boggy" area. The hairs do not fall out but can be pulled out without pain. However, pain due to secondary infection is not uncommon.
Treatment of tinea capitis involves oral antifungals, as topical preparations do not penetrate the hair shaft and therefore have no effect on the active organisms. The only antifungal preparation licensed for use in children in the UK is griseofulvin. Terbinafine is also effective and may be used off licence (see Table 1).

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Management
To prevent tinea capitis from spreading, which it can do very easily, particularly to other family members or schoolmates, the following precautions should be taken:

  • The infected child should be kept away from school until active treatment is initiated.
  • All sharing of combs, hairbrushes, hair accessories and head gear must be stopped.
  • The rest of the family should be treated with an antifungal shampoo (either ketoconazole or selenium sulphide) to help cut down the level of active spores and prevent cross-infection.(3)

Once tinea capitis has been diagnosed by taking and analysing a sample (see Box 1), oral antifungals can be commenced.
If kerion are present, action may be needed to relieve the discomfort caused by the tight crusts. This can be achieved by applying gauze soaked in warm water or antiseptic (such as a weak solution of potassium permanganate) to the lesion, leaving it for a few minutes, and then gently lifting the softened crust. In order to soften the crust sufficiently to lift it, the soaked gauze may need to be applied up to four times a day. The remaining open lesion may need to be dressed to prevent contamination by pathogenic organisms. If the lesion is particularly painful, oral analgesia should be considered.

Tinea pedis
Otherwise known as athelete's foot, this condition is most commonly seen in male adults and, as the name suggests, is particularly prevalent in men who play a lot of sport. The warm, sweaty (moist) environment created by sports shoes is ideal for fungal infections. Transmission is enhanced by the sharing of showers and changing facilities often found in sports clubs.
The most usual presentation of tinea pedis is a slightly scaly, itchy lesion in the 4th and 5th interdigital space. This may be accompanied by redness, cracks in the skin and/or a white macerated area. While tinea pedis is rarely more than an annoyance in fit and healthy adults, in the elderly it can provide the ideal entry lesion for pathogenic bacteria. This can lead to cellulitis or erysipelas (an acute febrile disease with localised inflammation and redness of the skin and subcutaneous tissue accompanied by systemic signs and symptoms).
Less commonly, tinea pedis presents as a scaly condition on other parts of the foot. The "moccasin" pattern shows pink scaling up the sides of the foot. White scaling on the soles of the feet, particularly of the skin creases, is caused by a particular fungus called Trichophyton rubrum. It may be unilateral or bilateral and can cause itching and/or soreness. It is often associated with fungal infection of the toenails.(4)

Management
Encouraging good foot hygiene is the best way of preventing tinea pedis. Meticulous attention to washing, and perhaps more importantly drying between the toes, will help to decrease the likelihood of an infection. Appropriate footwear is also a consideration. Open-toed sandals and no socks will help to keep the feet cool and thus decrease the likelihood of infection, whereas nonleather shoes and nylon socks are likely to create sweaty feet and a much higher risk of tinea pedis.
Treatment involves careful washing and drying of the feet and application of a topical antifungal cream for up to two weeks. It is important that the cream is continued even once the rash has gone, to ensure that all fungal spores are treated. For people who suffer recurrent infections, the use of antifungal powder (applied after washing and drying) may be helpful as a prophylactic measure.(5)

Tinea corporis and tinea cruris
Tinea corporis (ringworm of the body) is usually characterised by annular (ring-like) lesions, often just one or two, although lesions can occur more extensively. The rings appear as pink scaly plaques or papules that extend outwards, healing from the centre. The edge of the lesion is the "active" part, which explains why samples must be taken from the leading edge (see Box 1). They are generally unilateral (which helps to distinguish it from other conditions such as psoriasis and eczema that tend to be bilateral). Tinea corporis is often caught from pets, particularly puppies and kittens, and is caused by a zoophilic organism. Itching may occur.
Tinea cruris (ringworm of the groin and upper thighs) is caused by an anthropophilic organism and is more common in men than women. It manifests as a scaly red lesion usually starting in the groin flexure and moving out. Itching is common and can be severe. Tinea cruris often recurs, probably due to some level of autoinfection from another part of the body, such as tinea pedis.

Management
Topical antifungal preparations are appropriate for both these conditions. It is of key importance in tinea cruris that other fungal infections are treated simultaneously. Tinea pedis is usually the main culprit for autoinfection.
If ringworm infections are wrongly diagnosed as eczematous lesions and topical steroids are prescribed, the presentation of the lesion changes to become less scaly and more symmetrical. This is known as tinea incognito.

Tinea unguium
This is a dermatophyte infection that affects the nail plate itself, causing the nail to become thickened and discoloured. Infection is more common in toenails than fingernails and may start off on just one toe but is likely to spread. The growth rate of the nail slows down.

Management
For just one or two affected nails an antifungal nail lacquer may be sufficient. However, infection in more than two nails warrants oral antifungal treatment.

Yeast fungal infections
Yeast infections are caused by commensal fungi that become pathogenic under certain conditions. Two common yeast infections are considered here: pityriasis versicolor and candidiasis.

Pityriasis versicolor
This infection is caused by a species of yeast known as Pityrosporum. The rash is characterised by patches of slight scale on the upper trunk, upper arms and neck. In pale skin the rash will appear as a "dirty" brown colour, while in darker skins it will appear as hypopigmented lesions.(6)

Management
Treatment for pityriasis versicolor involves topical treatments, unless an individual suffers from recurrent infections, in which case oral antifungals may be used (see Table 1).

Candidiasis
Candidiasis is most commonly caused by Candida albicans. It can affect many different parts of the body but has a preference for moist, warm areas, including mucous membranes, flexures and interdigital spaces. Some of the most common sites of infection include:

  • The mouth, where whitish creamy patches peel off to reveal a red, bleeding base. This is most common in babies and children, the elderly, those who are immunocompromised, and patients on antibiotics or steroids (including inhaled steroids).
  • The genitals, where in women there is a creamy-yellow discharge accompanied by itching. In men the glans of the penis becomes red and inflamed and infection is accompanied by white cheesy plaques. Men can carry the infection without symptoms and may be the source of infection for their partners. In women, treatment with an imidazole pessary is usually necessary.
  • The napkin area in babies, where commonly candida is a secondary infective agent to nappy rash. It is characterised by a red glazed appearance with satellite pustules.
  • The flexures, which like the napkin area are characterised by glazed red lesions with satellite pustules.
  • The nails, where damage to the cuticle (often caused by repeated wet work) allows penetration of the fungal infection under the nail. This chronic form of the condition causes ridges to develop in the nail as the nail matrix is adversely affected. The only real way to treat the condition is to prevent the infection penetrating under the nail - wearing gloves when doing wet work will help, as will applying a layer of greasy ointment such as Vaseline around the nail several times a day.

It may be impossible to prevent yeast infections from developing because the systemic health of the individual has such a bearing on susceptibility to this type of infection. However, it is vital that nurses are vigilant to the early signs and symptoms so that an individual can receive treatment early before the infection has a significant impact.

Conclusion
Fungal infections of all types, with the exception of tinea capitis, prefer warm, moist environments to develop. Nurses can help patients to prevent the development of infections by encouraging good skincare, including washing and drying to maintain the effective barrier function of the skin. Treatments for fungal infections of the skin usually require the application of a topical cream, which must be applied in sufficient quantities for the correct period of time to have the desired effect. The exceptions to the topical route include fungal infections of the scalp (tinea capitis) and fungal infections of the nails, both of which require oral antifungal treatment. Patients may feel embarrassed at having a fungal infection and will need reassurance that treatment is possible and that it is unlikely there will be any long-term effects. Treating tinea capitis and tinea unguium will require prolonged courses of treatment. Patients must be reminded that for maximum therapeutic benefit they must complete the course as prescribed.

References

  1. Fuller LC, Child FJ, Midgley G, Higgins EM. Diagnosis and management of scalp ringworm.BMJ 2003;326(7388):539-41.
  2. Higgins EM, Fuller LC, Smith C. Guidelines for the management of tinea capitis. Br J Dermatol 2000;143:53-8.
  3. Winsor A. Tinea capitis - a growing headcount. Br J Dermatol Nurs 1998;2(3):10-12.
  4. Ashton R, Leppard B. Differential diagnosis in dermatology. Oxford: Radcliffe Publishing; 2005.
  5. BMA and Royal Pharmaceutical Society of Great Britain. British National Formulary 49. London: RPSGB; 2005.
  6. Graham-Brown R, Bourke JF. Mosby's color atlas and text of dermatology. London: Mosby; 1998.

Resources
dermatology.co.uk
An independent website providing an educational resource for skin conditions and their treatment for patients, the public and health professionals
W:www.dermatology.co.uk

DermNet NZ
W:www.dermnetnz.org

Emedicine
Dermatology pages
W:www.emedicine.com/derm

Prodigy
A source of clinical knowledge, based on the best available evidence, about the common conditions and symptoms managed by primary healthcare professionals
W:www.prodigy.nhs.uk