From Polish Stains to Health Clues: What Nail Discoloration Can Mean

A yellow tint might just be from your favorite polish, but a new dark streak deserves a closer look. Dermatologists explain the most common causes of nail color changes, and which ones call for a checkup.

Have you noticed any strange discoloration on your nails? Maybe a yellowish tint, a white spot, or a dark line? It’s not uncommon, but there are many reasons it can happen.

According to board-certified dermatologist Dr. Dana Stern, “discoloration” is a catch-all term for a nail that has “some kind of color variation from what is considered the normal nail appearance.” Stern says this can mean many different things, some harmless, some needing a closer look.

One of the most common, and harmless, causes of discoloration is nail polish. Darker shades, especially when used without a base coat, can leave nails with a yellowish tint. Smoking can also turn nails yellow, and nails tend to yellow with age, too.

If you see brown stains on your nails, they could be from products you’ve come in contact with, like tanning products or turmeric. White patches on your toenails can appear after wearing polish for long periods, while a dark mark may be due to blood under the nail from an injury.

Sometimes, discoloration in the nails can be due to something that needs more serious attention, for instance, an infection. A fungal infection can register as a tint of yellow or brown and can cause the nails to become brittle. A greenish tint on the nail can also be due to a bacterial infection.

Apart from an infection, your nail color can also say a lot about what’s going on in your body. According to the American Academy of Dermatology, pale nails may be a sign of anemia, bluish nails can be due to low oxygen levels, and yellow nails that thicken and stop growing can be a symptom of lung disease or other conditions.

If a fingernail or toenail develops a new or changing dark streak, the AAD advises seeing a dermatologist to check for skin cancer. Not every dark streak is cancer, but it could be melanoma, the most serious type of skin cancer, and catching it early can make treatment easier.

Because there are many reasons behind nail discoloration, Stern recommends seeing a dermatologist when you notice one rather than guessing. Take clear photos of your nails before your appointment and keep track of the affected nails and any changes. It also helps to recall any changes in your diet, weight, or medication, so your doctor can make a more informed assessment.

To prevent nail discoloration due to nail polish, use a base coat before applying the polish. Avoid wearing polish for long periods, too. If you get acrylics or other enhancements, choose an experienced nail technician, since bacteria can grow in moist spaces under a lifted nail.

Nutrition matters, too. Since nails are made mainly of a protein called keratin, getting enough protein supports nail health, says Jennifer Hanway, a board-certified holistic nutritionist. But she cautions against taking biotin supplements on a hunch, since evidence of their benefit is limited for people without a deficiency, and high doses can interfere with some lab tests.