Nail psoriasis

What it is

Psoriasis can affect nails.

How it works

Inflammation of the nail matrix and bed causes pits, lifting and thickening.

Why it matters on darker skin

Can be mistaken for fungus.

Causes and triggers

Psoriasis, trauma.

What helps — and why it works

Doctor diagnosis: treatment differs from fungus. Keep nails short: reduces trauma.

More detail

About half of people with skin psoriasis have nail changes at some point, and nail changes are even more common in people with psoriatic arthritis. Typical signs are small pits like the surface of a thimble, yellow-brown 'oil drop' patches under the nail, lifting of the nail from its bed (onycholysis), crumbling and thickening, and debris under the tip. Because these changes can look like fungal infection, a doctor may take a clipping to check before treatment. Treatments include strong steroid or vitamin D preparations applied to the nail fold, injections into the nail fold, and, for severe or arthritis-associated disease, tablets or injections that treat the whole body. Keeping nails short, wearing gloves for wet and dirty work and avoiding manicure trauma all reduce flares, because injury can trigger psoriasis in that spot.

What to avoid and why

Avoid antifungals without confirmation.

Common mistakes

• Assuming all thick nails are fungal.

Everyday nail habits

Healthy nails depend on protecting the nail matrix — the growing area hidden under the cuticle — and on limiting cycles of wetting and drying. Wear gloves for washing and cleaning, keep nails short and filed in one direction with a fine file, and moisturise hands, nails and cuticles after washing and at night. Leave the cuticle in place: it is a seal that keeps water and germs away from the matrix, and cutting it is a common cause of infection. Fingernails grow about three millimetres a month and toenails about one, so a new fingernail takes four to six months and a toenail up to eighteen months; any treatment needs at least that long to judge. Choose salons that sterilise metal tools between clients, or bring your own. Take breaks between gel or acrylic sets, and never peel coatings off. Because polish can hide important changes, look at bare nails regularly, particularly for a new dark band, a lifted nail or a change in shape.

Products and treatments

Many nail products make claims with little evidence. Moisturisers containing urea, lactic acid or petrolatum have the most support for dry, brittle nails and cracked skin around them. Formaldehyde-based hardeners can make nails more brittle over time and can cause allergy, so we do not recommend them. Antifungal nail lacquers such as amorolfine or ciclopirox can help mild fungal infection limited to the tip of one or two nails, but only after the diagnosis is confirmed — many thick or discoloured nails are not fungal at all. Biotin supplements are widely sold; evidence is weak and high doses can interfere with some blood tests. If you have diabetes or poor circulation, foot and toenail problems deserve early professional care.

Questions to ask your doctor or pharmacist

Useful questions include: What do you think is causing this? Is it likely to come back, and how can I prevent it? Which products should I stop? How long before I should expect improvement, and when should I come back if it isn't better? Are there side effects to watch for? Is this treatment safe if I am pregnant, breastfeeding or for my child? Writing your questions down, bringing your products (or photos of their labels) and taking dated photos of the problem make an appointment much more useful.