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Fungal foot conditions

By Asha Fowells

From the moment a baby stands up for the first time, his or her feet will be under constant strain, and the average person will walk the equivalent of twice round the world during his or her lifetime. Yet despite the hard work they do, feet are often poorly cared for and are a common reason for pharmacy consultations. This article will look at two fungal foot infections — athlete’s foot and fungal nail infections — that may be treated using over-the-counter products although in certain circumstances patients should be referred to their GP.

Athlete’s foot

Athlete’s foot (tinea pedis) is predominantly caused by the dermatophytes Trichophyton rubrum, Trichophyton mentagrophytes and Epidermophyton floccosum. The condition gets its common name from the fact that the fungus thrives in moist conditions, such as those that exist in footwear used for sport. The condition can affect anyone, although men and teenagers tend to be most commonly afflicted.

Athlete’s foot is spread by sufferers shedding infected skin scales that are then picked up by other people, for example, by walking barefoot in communal changing facilities (such as swimming pools) or by sharing towels or bathmats.

The risk of transmission can be reduced by wearing protective footwear in public places, such as flip flops in changing rooms, not sharing towels and washing them frequently, and avoiding scratching to reduce shedding of skin.

Other measures that can be taken to prevent the condition developing include wearing footwear that keeps the feet cool and dry, wearing socks made from cotton rather than from synthetic fibres, not wearing the same pair of shoes every day, and drying the feet thoroughly — paying particular attention to between the toes — after they have been washed.
There are three main types of athlete’s foot — interdigital disease, and moccasin and vesicobullous athlete’s foot.

Interdigital disease affects the toe webs, most commonly between the fourth and fifth toes. The skin becomes scaly or macerated, then peels and eventually cracks. Itching is common, particularly when footwear is removed.
Moccasin athlete’s foot affects the bottom of the foot or the heel. The skin appears dry and scaly, with pink, tender skin underneath, and the infection may spread to the toenails or the hands. This type of athlete’s foot is more common in people who suffer from atopic diseases.
Vesicobullous athlete’s foot usually starts with a crop of fluid-filled blisters, and most commonly affects the sole of the foot. A second crop of blisters may occur, and may involve other areas of the body such as the arms, fingers or chest. The symptoms are caused by an allergic reaction to the fungus and this form of the condition is most common in individuals who suffer from chronic interdigital athlete’s foot.

Before recommending any treatment, other conditions with a similar appearance, such as dermatitis, plantar keratosis or pustular psoriasis, or bacterial infection, should be excluded. Diagnostic tests are not usually required, but fungal sampling may be performed if the diagnosis is unclear, usual treatments have proved ineffective or oral treatment is being considered. Patients presenting with athlete’s foot symptoms that warrant referral to their GP include children, those with diabetes or suspected secondary infection, or if symptoms are severe, have spread beyond the toes to the nails, top or sole of the foot, or have not resolved following OTC treatment. Remember that pregnant and breast-feeding women are advised to use most OTC products with caution.

For mild cases of athlete’s foot, there are several OTC antifungals available. Each differs in the frequency of application and duration of treatment, so refer to the product packaging as necessary, but the skin should be washed and dried thoroughly before applying any treatment.
Several imidazoles are available to purchase, some in combination with hydrocortisone for skin that is particularly inflamed and sore. Imidazoles need applying for a week or longer after the symptoms have resolved, in order to ensure the fungus has been sufficiently treated — again the product packaging should be read carefully.

For the same reason, griseofulvin products also need using for a week or so after all signs of athlete’s foot have disappeared. OTC products containing terbinafine are popular because of their short duration of use, thanks to the fact that the antifungal remains in the skin after treatment has finished and can provide several months of protection against further outbreaks. Other OTC antifungal products for athlete’s foot contain the antifungals tolnaftate and undecanoates.

Oral antifungals are usually prescribed in cases where OTC treatment has failed, or if symptoms are severe. Terbinafine is normally the first choice, due to its favourable side effect profile, low incidence of interactions with other medicines, and treatment length (two to four weeks), which is shorter than with other oral antifungals, such as griseofulvin and itraconazole.

Fungal nail infections

Fungal nail infections (onychomycoses) are caused by a range of dermatophyte (most commonly Trichophyton rubrum and Trichophyton mentagrophytes) and non-dermatophyte moulds (such as Aspergillis, Fusarium, Scopulariopis and Acremonium species) and yeasts such as Candida species. They can involve any part of the nail, including the plate, bed and root, and toenails are much more commonly affected than fingernails. As the infection takes hold, the nail slowly discolours, starting at the tip and spreading towards the base, before distorting, thickening and sometimes crumbling. Onychomycosis is more common in people with fungal skin conditions, psoriasis or compromised immune systems, and the risk is increased by wearing tight footwear, warm, damp conditions or following trauma to the nail, such as stubbing the toe or cutting the nail too short.

There are several different types of fungal nail infection: distal lateral subungual onychomycosis, superficial white onchomycosis, proximal subungual onychomycosis, candida onychomycosis and total dystrophic onychomycosis.

Distal lateral subungual onychomycosis is the most common type of fungal nail infection. White or yellow opaque streaks appear along one side of the nail, due to skin and nail fragments accumulating under the nail. The nail may crumble, split or lift from the skin. If it affects the toenails, the condition can make wearing shoes uncomfortable.
Superficial white onychomycosis features small, flaky white patches and pits on the top of the nail plate, with the nail becoming rough and crumbly.
Proximal subungual onychomycosis is sometimes confused with white spots caused by injury, as it manifests with white or yellow spots in the half moon (lanula) and growing end of the nail. The skin may thicken and separate from the nail. The condition is more common in HIV-positive patients.
Candida onychomycosis (sometimes called paronychia) features redness and swelling next to the nail, possibly with pus present, and is more painful than other forms of onychomycoses. It affects the fingernails more commonly than the toenails.
Total dystrophic onychomycosis involves total destruction of the nail.

Fungal nail infections are usually diagnosed by the appearance of the nail, with discoloration a key indicator. Differential diagnoses include psoriasis, lichen planus, eczema, bacterial infection, onychogryphosis (scaling under the nail causing it to thicken), onycholysis (separation of the nail from the nail bed), viral warts, subungual melanoma and alopecia areata. To confirm the diagnosis of onychomycosis ahead of treatment, nail clippings or scrapings should be sent for fungal microscopy and culture, though there is a high incidence of false-negative results. Treatment is not always necessary — for example, for those who want to avoid drug treatment or who are simply not bothered about the condition — but should be considered if walking is uncomfortable, or if the person is at high risk of secondary bacterial infection due to a compromised immune system or the onychomycosis is thought to be causing a fungal skin infection. The pros and cons should be clearly outlined before embarking on treatment, including the fact that the appearance of the nail may not return to normal, cure rates are thought to be 60-80 per cent, the need to persist with medication for several months, and the risk of side effects.

OTC amorolfine nail lacquer can be recommended for adults over the age of 18 years who have distal lateral subungual onychomycosis affecting a maximum of two nails. The nail surface must be filed and swabbed before the product is applied and the process repeated weekly. While treatment is ongoing — and toenails can take up to a year to cure — nail varnish and false nails cannot be used, and the patient should be reviewed every three months.

Patients who require GP referral include anyone aged under 18 years, people with diabetes, pregnant or breastfeeding women, those in whom more than two nails are affected, and those for whom anything other than distal lateral subungual onychomycosis is suspected.

Amorolfine nail lacquer can be prescribed for patients with more than two affected nails, although oral terbinafine is usually preferred and visible improvement is usually apparent after three months of treatment. As an alternative to terbinafine, oral itraconazole may be used as pulsed therapy - one week on, three weeks off, repeated at least three times), though it is used first-line for candida onychomycosis.

Citation: Community Matters URI: 11106182

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