What Your Nails Can Tell You About Your Health

Your nails do more than you think: they enhance touch, protect fingertips, and can signal health problems. Learn how nails grow, what changes to watch for, and how to keep them healthy—plus tips for safe salon visits.

What do rams’ horns and birds’ beaks have in common with your fingernails and toenails? They’re all made of a protein called keratin, as is your hair and epidermis (the top layer of your skin).

Human nails serve several important functions:

• Enhancing touch, grip and precision for better fine motor skills
• Protecting the sensitive tips of your fingers and toes from injury
• Serving as tools for scratching and grooming

How Nails Grow

Nail growth begins under your skin, in the nail matrix located below the cuticle. As new cells grow, older cells divide, die, harden and are pushed out. By the time a nail emerges from below the cuticle, it is made up entirely of dead cells, which is why it doesn’t hurt to cut your nails.

Nails grow continuously. Fingernails grow approximately 0.003 to 0.004 inches a day. Toenails grow 0.001 to 0.002 inches a day. A full fingernail takes four to six months to regrow. A full toenail takes nine to 18 months. Not everyone’s nails grow at the same rate. Growth rate is affected by:

• Gender: men’s nails grow faster
• Hand dominance: the nails on your dominant hand grow faster
• Time of year: nails grow faster in the summer
• How much you use your hands: if you work with your hands, even by typing on a keyboard, the motion promotes blood circulation, which stimulates nail growth
• Health and nutrition: for healthy nails, eat plenty of protein and get enough iron, zinc, omega-3s, and vitamins B and C

Nail Changes Your Dermatologist Needs to See

If your nails develop a change in color, texture or shape, it could be a sign of a health problem. If you notice any of the changes listed below, see a board-certified dermatologist:

• A dark line or streak on a fingernail or toenail could be melanoma and requires an immediate doctor visit for a skin cancer check. Not every dark streak is melanoma, but it’s worth getting checked out ASAP. When caught early, melanoma is highly curable.
• When a fingernail starts to detach from the nail bed, there are several possible causes. It could be psoriasis, a fungal infection or the result of an injury.
• Redness and swelling around a nail are signs of infection. This can be treated early with soaking and topical antibiotics, but once an open sore forms, you’ll need more aggressive treatment.
• If a nail turns a greenish-black color, that’s a symptom of a bacterial infection and it won’t resolve on its own.
• “Pitted” nails have small dents that look like they were made by a tiny pick. This could be a sign of eczema or an autoimmune disease such as psoriasis, alopecia areata or lichen planus. A dermatologist can determine the cause.
• Yellow nails can be due to smoking or even wearing red nail polish without a base coat. However, if your yellow nails thicken and stop growing, it could be a sign of psoriasis or lung disease.
• Horizontal lines, called Beau’s lines, can have a variety of causes, all of which should be discussed with your doctor. Injury to the nail bed, illness or severe stress can interrupt nail growth and cause Beau’s lines. These may also occur with COVID-19, heart attack, measles, mumps, strep or pneumonia. Beau’s lines are also linked to chronic conditions such as diabetes, hypothyroidism, peripheral artery disease and Raynaud’s phenomenon. Vertical lines on the nail bed are generally harmless and tend to appear as we age.
• So-called “ram’s horn nails” are thick, overgrown nails that curl down. This is more common with toenails and can be due to a foot injury, psoriasis, peripheral artery disease or rare diseases such as ichthyosis or tuberous sclerosis complex. Ram’s horn nails can run in families and are more common in older adults. Cutting and treating these nails requires the assistance of a podiatrist or dermatologist.
• Thin, spoon-shaped nails that dip in the middle are a sign of an iron deficiency due to poor nutrition, celiac disease or stomach or intestinal issues.
• Clubbed nails are soft and spongy, curve downward, and are often accompanied by swollen and bulbous fingertips. Clubbed nails can be a symptom of a variety of serious illnesses affecting the heart, lungs, liver, bowels or thyroid. If your nails have a clubbed appearance, see a dermatologist right away.

Tips for Safe Salon Visits

Going for a manicure is a fun way to pamper yourself, but nail salons can be a breeding ground for pathogens ranging from nail fungus to staph, HPV and even hepatitis. Follow these tips to make sure you don’t come home with more than a pretty manicure:

• Choose salons that show a current state license and make sure technicians are also licensed by the state board.
• Check for cleanliness and sterilization. Make sure the salon is clean (visit the bathrooms), uses disposable tools, sterilizes foot baths and uses an autoclave (a high-pressure steam sterilizer).
• Consider bringing your own manicure/pedicure tools.
• Don’t shave your legs for 24 hours before a pedicure since bacteria can enter your system through a break in the skin.
• Limit or completely avoid gel and acrylic manicure. Removal can damage the nail plate, and the chemicals used to remove them dry out the nail and surrounding skin and can seep into your bloodstream. If you must use gels or acrylics for a special occasion, don’t leave them on too long. This can cause moisture buildup and lead to a fungal infection.
• Learn about carcinogens in nail glue. In addition to alcohol, cyanoacrylate and photo-bonded methacrylate, nail glue can contain formaldehyde.
• Put a high-SPF sunscreen on your hands before your appointment. The dryers used to harden gel nails emit ultraviolet light, which is linked to melanoma risk.

This article first appeared in the May 2026 edition of the HealthPerks newsletter.