Thickened, ugly nails are common – up to 10% of the population have infected toenails – but can be very upsetting. Fortunately, there are now some fairly effective treatments available that can help even if you have had the problem for years.

Causes of Thickened Toenails

Physical damage to your toenail may cause it to be thick until the damaged area grows out. This is why thickening of the big toenails is common in young men, particularly football players. Old people also often have thickened, hard toenails, probably because of the damage they have sustained over the years and because their nails grow more slowly, it takes longer to repair the damage.

Fungal infection can make your nails thick. The commonest infection is with Trichophyton rubrum, the same fungus that causes athlete’s foot. Occasionally, other types of fungus, such as yeasts, are responsible, and people who have been abroad may have some quite exotic fungi. (Fungal nail infections are also known as onychomycosis.)

Psoriasis, a skin condition, can make nails thick, with tiny pits on their surface. It is not a fungal infection but can look like it. However, if your nails are affected by psoriasis, they are also vulnerable to fungal infection.

How a Fungal Infection Occurs

It is easy to pick up fungi – they are particularly common on the floors of communal showers and changing rooms – and many of us probably already have fungi on our skin. They cause problems only when the conditions are right for them to thrive, which means warmth and moisture. When human beings started wearing enclosed shoes, which trap sweat and heat, we created ideal conditions for fungi. This is why only 1% of people in Zaire, Africa, have fungal toenail infections compared with 10% of people in the UK. It is not surprising that fungal toenail infections (and also athlete’s foot) are five times as common in people who have to wear work boots for long periods in wet conditions.

The fungi shelter under the tip of the nail and start to get a hold. This is particularly likely to happen if:

  • the end of the nail has been damaged (for example, by ill-fitting shoes) and is already slightly separated from its toe
  • you are taking long-term tetracycline medication and then expose your toenails to sunlight – this is called photo-onycholysis
  • you have a condition such as diabetes or an immune deficiency
  • you are elderly
  • the fungus is already multiplying between the toes (athlete’s foot).

The fungus very gradually spreads towards the base of the nail and down the sides, loosening the nail from the underlying toe and filling the separated area with crumbly, yellowish-white gunk. The nail itself becomes thicker and yellowish brown in colour. This can take months or years.
Sometimes the infection starts at the base of the nail, giving a whitish area near the half moon, or it may just affect the surface of the middle of the nail, where it will appear as a white patch.

What You Can Do

Be patient. For any treatment to be successful, one of the most important elements is patience. You will have to use the treatment for at least 3 months, and some treatments take even longer to work. Nails grow from the base to the tip, as anyone who has used nail varnish knows. Because it can take 18 months for a nail to be replaced completely by a new one, it may be a long time before you see a result.

Try amorolfine, an antifungal nail paint that you can buy from pharmacies. It is usually applied once or twice a week after filing and cleaning the nails. Treatment should continue until the infection has cleared, which can take about 6 months for fingernails and up to 12 months for toenails. See ‘What your doctor can do’ below for further general information on nail paints.

Try benzalkonium chloride which you can buy from pharmacies. It is applied twice daily for 2–4 months for fingernails or 4–8 months for toenails. It is an antiseptic that kills some bacteria and fungi.

Tea tree oil, which is available from health shops and chemists, may be worth trying if you really do not want to go to your doctor. It has some natural antifungal properties and one study found that it improved or cured 60% of cases of toenail infection. Apply it generously twice a day with a cotton-wool bud, wiping it under the tip of the nail and on the surrounding skin. Because it is an oil, it may discolour leather shoes. At night, soak a small piece of cotton wool with the oil, and tape it to the end of your toe.

Is tea tree oil safe?

  • There have been concerns about the safety of tea tree oil, especially if undiluted.
  • The EU’s Scientific Committee on Consumer Products says the undiluted oil is a ‘severe irritant’ to the skin. And the risky chemicals become even stronger if the oil is stored at room temperature and exposed to light and air. Some experts advise using a concentration of only 1%.
  • Another study warns that using very dilute tea tree oil (perhaps less than 4%) can make skin bacteria resistant to antibiotics – ‘superbugs’ (Journal of Antimicrobial Chemotherapy 2007;59:125–127).

Care for your feet sensibly by following these rules.

  • Give your feet plenty of air, because warmth and sweat encourage the fungi; so follow the advice given for sweaty feet. When you are at home, go barefoot whenever possible, and if you don’t want to expose your toenails search for some strappy sandals that cover the toes.
  • Choose shoes that give your toes plenty of room. As well as making sure your shoes are long enough, so your toes are not touching the end, check there is plenty of depth in the toe area. You don’t want shoes that compress your toenails. Hold the shoes up and look at them sideways, and when you are trying them on wiggle your toes upwards to check there is room.
  • Dry your feet very thoroughly after washing, using a tissue to dab underneath the end of the nail to make it as dry as possible.
  • It is tempting to use nail varnish to disguise the nail, but nails need to breathe so use it for short periods only, removing it as soon as possible.

Treat athlete’s foot promptly. If you ever develop athlete’s foot in the future, treat it so it does not spread to the nails.

How a Chiropodist Can Help

For any problem with your feet, particularly the toenails, it is well worth seeing a state-registered chiropodist – in the UK, a qualified chiropodist will be registered with the Health Professions Council. The chiropodist will be able to advise you on foot care, and will be able to tell you if your thickened toenail is likely to be a fungal infection or due to some other cause. The chiropodist can also thin down the thickened nail so that other treatments such as paints or tablets will be more effective. Chiropodists cannot prescribe antifungal tablets or the most effective antifungal paints – you will have to see your family doctor for these.

What Your Doctor Can Do

There are now some quite effective treatments for fungal nail infections. The downside is that they have to be taken for a long time, can have side effects and do not work for all types of fungi. So before starting treatment your doctor will usually take a sample by scraping under the nail and on the nail surface (this may be slightly uncomfortable but not painful) as well as a clipping of the diseased nail and will send it to the laboratory to identify your particular fungus. It can take over 3 weeks for the laboratory to grow and identify the fungus.

Antifungal nail paints. If only the end of the nail is affected, the nail is not too thick and the cause is a Trichophyton fungus, your doctor may prescribe a nail paint. There are various types of nail paint. As well as the over-the-counter product amorolfine (see above), there are a couple of nail paints for which you need a doctor’s prescription:

  • 28% tioconazole, which is applied twice a day for 6 months.
  • Ciclopirox, which is used in the USA but is not available in the UK.

It is important to use nail paints continually because if you stop, even for a short period, the new nail that has grown will become infected by the fungus, and you will be back to square one. Antifungal paints are not suitable if you are pregnant. Success rates are not very high – possibly 40% for amorolfine, about 22% for tioconazole and about 12% for ciclopirox. Although inconvenient, they do have an important plus point; you apply the drug only to the part of the body where it is needed, rather than taking a tablet that could have side effects.

Medications that you swallow. Your doctor may prescribe itraconazole or terbinafine for certain types of suitable fungus shown on the laboratory test.

  • Itraconazole is taken twice daily for a week, followed by a 3-week medication-free period. The treatment saturates the nail and continues to work in the medication-free period. This treatment cycle is repeated two more times.
  • Terbinafine is taken every day for about 3 months, or in a higher dose for 1 week each month for 3 months. The continuous treatment is probably more effective (Journal of the American Academy of Dermatology 2005;53:578–584; National Institute for Health Research).

The treatment does not have an immediate effect. The drug stays in the nail and continues to act long afterwards, and the result shows when the new healthy nail grows.

Experts are arguing about how effective these drugs are. Some claim that they have a 80–95% likelihood of cure, but the true figure may be lower – probably 25–40% for itraconazole and 35–50% for terbinafine (Archives of Dermatology 1998;134:1551–1554).

Like any drug, these medications can have unwanted side effects. There have been rare cases of severe reactions, and each of these drugs can affect the liver. The main side effects are headaches, itching, loss of taste, and diarrhoea. You should not take itraconazole if you are taking erythromycin (an antibiotic), or if you are taking calcium-channel blocking drugs (for angina or blood pressure). Also, itraconazole may weaken the force of the heart’s contractions, so you should not take it if you have a heart problem.
If the medication has not worked after taking it for the correct length of time, your doctor will consider other possible causes, such as psoriasis or another skin condition called lichen planus, or that your footwear is continuing to damage your toes.

Laser treatment is a promising new treatment and is already being used in the USA and the EU. More research needs to be done to find the best wavelengths to use and the best type of laser.

Photodynamic therapy uses special nail paints that penetrate the nail, followed by a special red light that activates the drug within the paint. The success rate so far is only about 43%.

Future treatments. A lot of possible new treatments for nail infections are being investigated (Expert Opinion in Pharmacotherapy 2012;13:1131–1142). Some of these may become standard treatments that you will be able to obtain from your doctor, but at the moment they are just being researched or are not widely available. One possibility is iontophoresis, which may help antifungal nail paints to be more effective. New drugs and new nail paints are in the pipeline; some of the paints contain terbinafine (see above).

Fascinating Facts

  • Nails are made of keratin, the same protein as horses’ hooves
  • It takes 12-18 months for a toenail to grow from root to tip
  • If you are right-handed, the nails on your right hand grow faster than on your left, but toenails grow at the same rate on each foot
  • Nails grow faster in summer than winter
  • Toenail problems have strange medical words. Onychogryphosis (on-ee-co-gry-foe-sis) is the thickened, hard toenails that old people often have: onychomycosis (on-ee-co-my-co-sis) means fungal nail infection
  • In the UK, the NHS spends more than £15 million a year on treatments for fungal nail infection


First published on:
Reviewed and edited by: Fiona Elliott
Last updated: January 2021

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