Fungal nail infections

A fungal nail infection thickens, discolours and crumbles the nail, usually starting at one edge of a big toenail and working back towards the base. It affects something like one adult in ten and becomes commoner with age. It is not dangerous in most people, it is not especially contagious, and it is one of the hardest ordinary conditions to treat successfully.

That last point is worth establishing before anything is bought. A great deal is sold for fungal nails, a good deal of it to people whose nails are not infected, and the people whose nails are infected routinely spend many months on a treatment that was never likely to work for the extent of disease they have.

First: the nail may not be infected at all

Roughly half of abnormal-looking nails turn out not to be fungal. The commoner impostors:

• Repeated minor trauma, which is probably the single commonest cause of thickened, ridged toenails. Shoes with a narrow toe box, running, and years of catching a toe on furniture all do it. The nail thickens and discolours and no fungus is involved.
• A bruise under the nail, from a single injury or from pressure. The giveaway is that the discoloured patch moves towards the tip as the nail grows, rather than staying put.
• Psoriasis, which produces pitting — small dents in the nail surface — and lifting of the nail from its bed. Nail psoriasis is common in people with psoriasis elsewhere and sometimes appears before the skin does.
• Chronic paronychia, where the skin fold at the base is swollen and the cuticle lost, usually from prolonged wet work.
• Lichen planus, eczema and ageing, all of which change nails.

There is one appearance that needs seeing promptly rather than treating. A dark pigmented band running lengthwise along a nail, particularly one that is widening, is in a single nail, has no history of injury, or where the pigment extends onto the skin at the base of the nail, can be a melanoma of the nail bed. It is uncommon and it is frequently mistaken for a bruise or a fungal nail, which is how it gets diagnosed late.

What a fungal infection looks like

Typically it begins at the free edge or the side of the nail and spreads towards the cuticle. The nail becomes white, yellow or brown, thickens, separates from the nail bed, and in time crumbles. Debris collects underneath. It is usually painless, though a thickened nail pressing inside a shoe can hurt a good deal.

The big toenail is most often first. Fingernails are affected far less often, and a fungal fingernail infection without any toenail involvement is unusual enough to be worth a second look.

It rarely arrives alone. Athlete's foot is present in most cases, usually in the skin between the toes or on the sole, and this matters: treating the nail without treating the skin means the nail is reinfected from a few centimetres away.

Who gets it, and how

The fungi responsible live in warm damp places and in shed skin. Communal showers, changing rooms and swimming pool surrounds are the classic sources, along with shared towels and shared nail clippers.

Risk rises with age, with diabetes, with poor circulation in the legs, with a suppressed immune system, with nail damage, with occlusive footwear worn for long hours, and with athlete's foot. Nail salons are a recognised route where instruments are inadequately sterilised, and artificial nails and prolonged nail varnish both create conditions that suit fungus.

On contagion: it spreads within households through floors and towels rather than through casual contact, so the common reassurance that someone with fungal nails is not infectious is broadly right and slightly too comfortable. Keeping to separate towels, separate clippers and footwear in shared bathrooms is sensible.

Treatment, honestly

Three things are true at once, and most writing on the subject admits only the first.

It can be treated. Treatment takes a long time and often fails. And not treating it is a legitimate choice, which UK guidance states explicitly — particularly for older people, and for anyone whose nails are not painful and who is not bothered by how they look.

Before oral treatment, the diagnosis is confirmed. Nail clippings and the debris from underneath are sent for laboratory examination. This is not bureaucracy: oral antifungals are taken for months, they have real side effects, and given that half of abnormal nails are not fungal, starting them on appearance alone means a substantial number of people take them for nothing. Anyone offered tablets without a sample having been sent is entitled to ask why.

Topical treatment — amorolfine lacquer, painted on weekly after filing the nail — is available from pharmacies without a prescription for up to two nails. Its place is narrow: mild infection affecting only the far end or edge of the nail, or cases where tablets cannot be taken. It is applied for nine to twelve months for a toenail. The evidence behind topical treatments is limited and the cure rates are modest, and that combination of a long commitment and a poor chance is why so many people conclude that nothing works.

What topical treatment cannot do is reach an infection that involves the base of the nail or most of its surface. Using it for that is the commonest wasted year in this condition.

Oral treatment is more effective and is what is used for anything extensive. Terbinafine is the usual choice, taken daily for twelve to sixteen weeks for toenails and about six weeks for fingernails. Itraconazole is the alternative, given as a week of tablets each month, repeated three times for toenails. Both interact with a number of other medicines, both need caution in liver disease, and terbinafine can affect taste and, rarely, the liver — which is why it is prescribed rather than sold, and why anyone taking it should report jaundice, dark urine or persistent nausea.

The nail will not look better when the treatment finishes. This is the point that causes the most unnecessary disappointment. The drug clears the fungus from the nail; the damaged nail itself has to grow out, and a toenail takes twelve to eighteen months to replace itself completely. A nail that still looks wrong three months after finishing a course has not necessarily failed.

Laser and other device treatments are marketed for this condition, often expensively. The evidence that they cure it is weak, and they are not part of NHS treatment.

Where a thickened nail is uncomfortable rather than unsightly, a podiatrist reducing and filing it is often more use than any antifungal, and that is a reasonable outcome in itself.

Prevention, and stopping it coming back

Recurrence is common, and the measures that reduce it are the same ones that prevent it in the first place:

• Treat athlete's foot, and keep treating it. This is the most important single thing, and the most frequently skipped.
• Dry between the toes after washing, properly, before socks go on.
• Footwear in communal showers, changing rooms and around pools. This applies to gyms and hotels as much as to residential care.
• Breathable socks, changed daily, and shoes allowed to dry out between wearings. Alternating two pairs is more effective than it sounds.
• Well-fitting shoes without a narrow toe or a high heel, which reduces the nail damage that lets fungus in.
• Nails kept short and filed down, cut straight across.
• Separate clippers, not shared, and cleaned. Clippers used on an infected nail will carry it.
• Antifungal powder or spray in shoes, which is cheap and reasonable where infection keeps returning.
• A salon that sterilises its instruments, and a pause on artificial nails and permanent varnish while a nail is recovering.

When to see someone, and when not to self-treat

Most people with a fungal nail can decide for themselves whether to bother. These are the exceptions:

• Diabetes, poor circulation in the legs, or a suppressed immune system. Foot infections in these groups can progress to cellulitis and worse, self-treatment is not appropriate, and foot problems should be assessed rather than managed at home.
• Numbness in the feet, from diabetes or any other cause, which means an injury or infection can develop without being felt. Feet in that situation need looking at regularly by someone, because looking is doing the work that sensation would otherwise do.
• Any dark pigmented line along a nail, or pigment spreading onto the skin at the nail's base — promptly.
• Pain, redness or swelling spreading into the toe or foot, which is an infection of the skin rather than the nail and needs treating.
• A nail that is painful, or thick enough to be a problem in shoes.
• Nail changes in a child, where fungal infection is uncommon and specialist advice is the route.
• No improvement after a full course of topical treatment, or after oral treatment plus the time needed for the nail to grow out.
• Pitting, or nails changing alongside a rash, which points at psoriasis or eczema rather than fungus and is treated differently.