What makes fingernails curve

National Library of Medicine noted. Lung cancer is the most common cause, although congenital heart defects, chronic lung infections, celiac disease, liver disease, Graves' disease and other conditions can also cause it. In clubbing, the nail may curve downward so it looks like the round part of an upside-down spoon, the National Institutes of Health NIH noted.

Usually, all of the nails are involved, not just one, Rich said. The condition affects fingernails more commonly than toenails, but she has seen it in both types. The last section of the finger may also appear large or bulging. The curved nails can develop quickly and may return to normal quickly when the cause of the health problem is treated, NIH added.

All doctors, including primary care doctors, should be able to recognize the symptoms, not just nail specialists, Rich said. Nail clubbing is also associated with inflammatory bowel disease, cardiovascular disease, liver disease and AIDS. There is a problem with information submitted for this request. Sign up for free, and stay up-to-date on research advancements, health tips and current health topics, like COVID, plus expert advice on managing your health.

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These can appear after really intense stress to your nail makes it stop growing or grow more slowly than usual for some time 2. This is called koilonychia, and it can be a completely normal age-related change to your nails, Dr. But it may also indicate iron-deficiency anemia or other disorders in which iron is not metabolized correctly, like hemochromatosis and Plummer-Vinson Syndrome, which happens after long-term, chronic iron-deficiency anemia 3.

But other times, this half-and-half white coloring can be a symptom of a more serious issue like chronic kidney disease 4. A dark brown or black stripe along your nail, or brown pigments surrounding the nail, will most often be benign moles or pigmentation. This is most common in people with darker complexions because they tend to have more pigment-producing melanocytes in their skin and nails 6.

Stern explains. This is especially the case if the dark streak is changing in some way, like widening or getting even darker. This is also key to keep in mind if you have dark skin, as you can be more vulnerable to getting melanoma on your hands and feet which can present on your nails.

Stern notes that most commonly, nails turn yellow because of nail polish use. Stern explains, and sometimes causing yellow nail syndrome.

If your nails are curving down and have a noticeable rounded edge—kind of like upside down spoons—this could be a sign of clubbing 8. Clubbing can even make the tips of your fingers appear swollen or bulging.