Nail Discolouration
Reviewed by Andrew Schox, BSc(Hons) PGradDipPod MPod, October 2026
Nail discolouration means any change in the colour of a nail. Nail problems make up about 10 per cent of skin problems and are more common in older adults. Common causes include fungal infection, nail psoriasis, injury, nail cosmetics, smoking and some medicines. Many causes are harmless and settle once the cause is dealt with. But a single dark band or patch on one nail that is new or changing needs a doctor's check without delay. Melanoma (a type of skin cancer) is rare, but it is the cause not to miss.
What is it?
Nail discolouration is any change in the colour of a nail. It can start in the nail itself, in the skin under it (the nail bed), or in the area at the base of the nail where it grows from (the matrix). The nail might turn yellow, white, green, grey, brown or black, and one nail or several can be affected.
A brown or black stripe or patch is called melanonychia. It comes from extra pigment in the nail. White nails are called leukonychia. Both names are used for what you can see, not for the cause.
Most nail changes are common and harmless. A few point to an infection, a skin condition or an illness elsewhere in the body, and one rare cause, nail melanoma, needs to be found early.
What can cause it?
The colour and pattern give clues, but they are only clues. One nail can have more than one cause, so your podiatrist will look at the whole picture.
Fungal nail infection (onychomycosis) is the most common nail infection in the world. It often causes a yellowish nail that becomes thick, crumbly and soft under the free edge, and may lift off the nail bed. It usually starts at the tip of the nail. Sometimes it shows up as a white, powdery patch on the surface of the nail.
Nail psoriasis is another common cause of yellow nails. Tiny pits in the nail and the nail lifting away from its bed point towards psoriasis rather than a fungus.
Injury and blood under the nail (a subungual haematoma) can turn a nail dark purple, brown or black after a knock or stubbed toe. As the nail grows, the dark patch moves forward towards the tip. Normal-looking nail appears behind it, between the dark patch and the skin fold at the base. Small white spots on the nail are also usually from minor injury.
Nail cosmetics, chemicals and smoking can stain or weaken nails. Frequent nail varnish can make nails brown. Artificial nails and frequent polish remover can leave fine, scaly white spots. Hair dyes and nicotine can also discolour nails.
Medicines can change nail colour. Some antibiotics, antimalarials and chemotherapy medicines are on the list, as is dithranol, a cream used for psoriasis. Some medicines can make nails grey, such as antimalarials or minocycline.
Harmless dark bands are a common cause of brown or black stripes. In adults, about 73 per cent of dark bands on a single nail come from pigment cells in the nail becoming more active, which is not dangerous. In children, almost all causes of dark nail colour are harmless and need no treatment.
Bacterial infection with pseudomonas can cause green-black discolouration, especially under a nail that has loosened.
Illness elsewhere in the body can sometimes show in the nails. White nails can have causes from simple manicure habits to serious liver or kidney problems. Brown nails can follow thyroid disease, pregnancy or poor nutrition. Nail changes can also be an early sign of lupus (an autoimmune condition), but they are not specific to it and cannot diagnose it on their own.
Nail melanoma is rare compared with fungal infection and bruising under the nail. It usually affects a single nail. The pigment may spread onto the skin fold around the nail. About 3 in 10 nail melanomas show up as a lump in the nail rather than a dark line.
Who gets it?
Nail changes can happen at any age, but they are more common in older adults. Nail problems make up about 10 per cent of skin problems.
There is no single figure for how many people have discoloured nails from any cause. Fungal infection is better studied. Often-quoted figures are about 10 per cent of people overall, 20 per cent of people over 60 and 50 per cent of people over 70. Some estimates are lower, so it may be less common than these figures suggest. It affects toenails more than fingernails and is more common in men.
You are more likely to notice colour changes if you wear nail varnish or artificial nails often, smoke, take certain medicines or knock your toes a lot, for example in running or sport.
How is the cause found?
Your podiatrist will start by looking carefully at all your nails, the skin folds around them and the surrounding skin. They check the shape and surface of the nails as well as the colour. They will ask when you first noticed the change and whether you have injured the nail. They will also ask about nail cosmetics, smoking, your medicines and any skin or general health conditions, including any history of skin cancer.
For a dark band or patch, they will also ask which nail it is on, whether it has changed, and how wide and dark it is. They may use a dermatoscope (a small light and magnifier) to look closer. This can help tell blood from pigment. It can also help sort marks that can safely be watched from those that need a small sample taken (a biopsy). Looking alone can't always be sure, so a suspicious mark needs a doctor's assessment. A doctor or specialist then decides whether a biopsy is needed.
If a fungal infection is likely, nail clippings can be sent to a laboratory to confirm it before treatment starts. If you have white nails on many nails, you may need blood tests to check for illness elsewhere in the body. If the cause stays unclear, you may be referred to a doctor or a skin specialist (dermatologist).
Treatment
The right treatment depends on the cause, so finding the cause comes first. Don't start antifungal treatment for a nail that is only discoloured. Yellow nails, for example, can be psoriasis rather than a fungus.
Looking after it at home
For small white spots, gentle nail care is usually all that is needed. Avoid pushing back or picking at your cuticles. Cut down on nail polish, polish remover, artificial nails and nail glue, which can irritate or weaken the nail.
White nails caused by a fungal infection usually need antifungal treatment instead.
Treatment from your podiatrist
Your podiatrist can trim, shape and care for a thickened or fungal toenail. They can also help work out the cause and arrange nail clipping tests. If the cause needs a prescription or a specialist, they will refer you to your GP or a dermatologist.
Treatment depends on what is found. Bacterial infections need antibiotics. Fungal infections are treated with antifungals, mainly tablets. Any skin condition contributing to the problem is treated too. For mild fungal infection on the surface or near the edges of the nail, a medicated nail lacquer (amorolfine) may be suggested.
For fungal toenail infection in adults, terbinafine tablets work much better than a dummy tablet. They also probably work better than other antifungal tablets (azoles), with the same risk of side effects. This is the best-supported treatment, but it has been tested mostly in adults with toenail infections. It may not apply to fingernails, children or nail colour changes with other causes.
These tablets are prescription medicines. They can interact with other medicines and can affect the liver. Severe reactions, including liver damage that can be fatal, happen in fewer than 1 per cent of cases. Your doctor will review your health and other medicines first, and take extra care if you have liver disease or an autoimmune condition. If you are pregnant, might become pregnant or are breastfeeding, get advice from your prescriber first.
Other options
If the first treatment doesn't work, your doctor may refer you to a dermatologist rather than repeat the same thing. This also applies if the cause is uncertain or a growth in the nail is suspected. Check that the nail really is a fungal infection before treating again.
In adults with toenail infections, tablets taken continuously (terbinafine or itraconazole) have better cure chances than medicated nail paints and creams.
Laser treatment has limited effect on fungal toenails. The combined clinical cure rates were 13.0 to 16.7 per cent for short-pulsed lasers and 25.9 per cent for long-pulsed lasers. People with diabetes should avoid laser treatment, which is typically not used because of the risk of burns and ulcers. They should also generally avoid surgical removal of the nail because of infection and ingrown nail risks. Gentle removal of the thickened nail by your podiatrist, with specialist guidance, is preferred instead.
Urea added to other treatment (a cream that softens the nail) has only been tested in small studies. Mild to moderate side effects have been reported, including softening of the skin around the nail, redness and tingling.
Will it get better?
It depends on the cause. Blood under a nail grows out with the nail. Darkening from a medicine usually fades slowly after the medicine is stopped. Harmless dark bands have a good outlook, and in children almost all dark nail colour is harmless.
Fungal infection can come back after treatment. It isn't yet clear whether any one prevention step lowers the chance.
Nail melanoma is the exception. Its outlook is poor, largely because it is often found late. Diagnosis is delayed by about 2 years on average. That is why a dark area under a nail that you can't explain, or a band that changes, should be checked without delay. Finding melanoma early makes it easier to treat.
Preventing it
You can't prevent every cause of nail discolouration, but there are sensible steps to reduce fungal infection. These steps are mostly expert advice rather than proven by trials. They include treating athlete's foot promptly, keeping your feet dry and cool, and not going barefoot in shared wet areas such as pool changing rooms. Replace old footwear or clean it well.
Older ways of cleaning shoes, such as boiling them or using chlorine and salts, are not very practical. They can also damage shoes and cause health problems.
To protect your nails from stains and weakness, go easy on nail varnish, remover and artificial nails. If you notice a new dark band, or a change in an existing band, don't wait. Go to your GP.
When to see a podiatrist
Book an appointment if
Book an appointment with your podiatrist if a nail has changed colour and you don't know why, if the cause isn't clear, or if a fungal nail hasn't improved with treatment. See your GP soon if your nails have changed in colour, texture, shape or thickness for no clear reason, or if many of your nails have turned white, as you may need blood tests. If you have diabetes, poor circulation in your legs or feet, or a weakened immune system, see your podiatrist or GP early for any nail change that could be a fungal infection. Nail infections can cause more serious problems in these conditions, and reduced feeling in your feet can hide nail damage.
Seek prompt assessment if
Get medical assessment without delay: see your GP promptly if you notice a single dark band or dark patch on one nail that is new, widening, darkening or spreading. The same applies if dark colour spreads onto the skin around the nail, if there is a dark area under a nail that wasn't caused by an injury, or if there is a lump in or under a nail. Be especially alert if it is on one nail only, particularly a thumb, index finger or big toe, and if you are in your 30s or older. These signs are most often caused by something harmless. Being checked is a precaution, and an urgent referral doesn't mean cancer has been found.
Frequently asked questions
Do dark stripes on my nails need checking if I have darker skin?
Dark stripes are very common in people with darkly pigmented skin, and nearly all black people develop one or more by age 50. They are usually harmless. But a single stripe on one nail, or any stripe that is changing, still needs a doctor's check.
My child has a dark nail. Should I worry?
Almost all dark nail colour in children is harmless and needs no treatment. If you're unsure what caused it, or if it changes, see your GP. When in doubt, it is always fine to ask for a check.
What do small white spots on my nails mean?
Small spot-like white marks are the most common kind of white nail change, especially in children. They are usually from minor injury to the nail. Fine, scaly white spots can also come from artificial nails or frequent polish remover. Gentle nail care is usually all that is needed.