A little-known sign on your nails may indicate health problems.

Fingernails and toenails are made of keratin, a very tough fibrous protein. Their function is to protect the tips of the fingers and toes and help develop motor skills. The appearance of nails is an important indicator of a person’s health, but we do not always pay attention to it or not enough. Naturally, the nails are pinkish in color, translucent and without stains. Healthy nails should be “smooth” and have “uniform color” explains Dr. Amir Khan, a doctor in the National Health Service (the United Kingdom’s public health system) in a video posted to his Instagram account. Conversely, the specialist warns that signs of poor health and even disease may be visible on the nails.

In his video, the doctor, who has nearly 400,000 subscribers, points out, for example, that nails that become very thick and crooked could be a sign of an inflammatory disease such as Crohn’s disease, ulcerative colitis or liver disease. The nails are dug in like “spoon” as Dr. Khan shows, it can be a sign of glandular anemia, lupus, or thyroid dysfunction. The latter disorder is also associated with nail splitting, also called “onycholysis.” Peeling nails may also indicate a fungal infection or psoriasis.

Seriously though, Dr. Khan teaches us in his video that an overlooked nail symptom could be a sign “cancer, fluid in the lungs, bronchitis or rheumatoid arthritis.” This symptom is called “yellow nail syndrome” : “This occurs when the nails turn yellow, become thicker, and no longer grow as quickly as before.”, explains the doctor. Yellow nail syndrome remains rare and is different from the yellowing of one or two nails that we may see in smokers (due to nicotine), or the yellowing of all nails after applying polish.

A change in the appearance of one or more nails alone is not enough to diagnose the condition, but can help a healthcare professional make a diagnosis by relating it to other symptoms. Therefore, it is important to pay attention to changes in the color or appearance of your nails and contact your doctor during your consultation. Finally, some nail changes are nothing to worry about. A blow can, for example, cause a hematoma to appear on the nail, and aging can cause small vertical streaks to form on the nails.