Brittle Nails: Why Nails Split and Peel

What brittle nails look like

Doctors describe a few distinct patterns:

Nails are made of layers of keratin held together by fats and water. Brittle nails have lost water and the "glue" between layers, so they flake and split.

Common causes

Repeated wetting and drying

This is the single biggest cause, especially in fingernails. Nails absorb water and swell, then shrink as they dry. Repeated cycles loosen the layers. Healthcare workers, cleaners, hairdressers, cooks, parents of young children and anyone handwashing often are prone to it.

Nail cosmetics

• acetone-based polish removers dehydrate the nail plate
• gel and acrylic nails require filing, soaking in acetone and UV curing, which thin and weaken the nail
• frequent polish changes and nail hardeners containing formaldehyde can make nails more brittle over time

Aging

Nails grow more slowly and become drier and more ridged with age. Vertical ridges are normal in older adults.

Environment

Cold, dry winter air and low humidity worsen brittleness.

Medical causes

Iron deficiency

Iron deficiency anemia can cause brittle, thin nails, and in more severe or long-standing cases, spoon-shaped nails that curve upward (koilonychia). Look for tiredness, breathlessness, pale skin, heavy periods or a restricted diet.

Thyroid disease

Hypothyroidism causes dry, brittle, slow-growing nails along with tiredness, cold intolerance, weight gain and dry skin. An overactive thyroid can cause nails to lift away from the nail bed.

Skin conditions affecting nails

• Psoriasis: pitting, lifting, oil-drop discoloration and crumbling, often with scaly skin patches. See psoriatic nails.
• Lichen planus: thinning, ridging and splitting, sometimes with permanent scarring of the nail.
• Eczema around the nails: irritated skin around the nail fold leads to ridged, uneven nails.

Fungal nail infection

Onychomycosis makes nails thick, discolored (white, yellow or brown) and crumbly, usually starting at the tip. It is much more common in toenails.

Other causes

• poor circulation, including Raynaud's phenomenon
• low zinc, protein deficiency, eating disorders and malabsorption
• chemotherapy and retinoid medicines
• injury to the nail
• rarely, conditions such as amyloidosis

Clues that point to a medical cause

How brittle nails are assessed

Most brittle nails need no tests. A doctor or dermatologist will ask about handwashing, chemicals, manicures, diet, medicines and other symptoms, and look at all nails and the skin. Depending on what they find, they may order:

• a blood count and ferritin for iron stores
• thyroid function tests
• nail clippings for fungal culture or microscopy before treating a fungal infection
• occasionally, a nail biopsy

Treatment and home care

Nails grow slowly: fingernails about 3 mm a month, toenails about 1 mm. Any improvement shows only as new nail grows out, so allow 4 to 6 months for fingernails and 12 to 18 months for toenails.

Daily nail care

• Moisturize nails and cuticles several times a day and after every handwash, with a thick cream or ointment. Products containing urea, lactic acid or lanolin are useful. Rub it into the nail plate and fold.
• Wear gloves for dishwashing and cleaning: cotton liners under rubber gloves.
• Keep nails short and file in one direction with a fine emery board. Round the tips slightly.
• Use an acetone-free remover no more than once or twice a month.
• Take breaks from gel and acrylic nails.
• Do not use nails as tools for opening cans or scraping.

Supplements

• Biotin: small studies suggest it may help some people with brittle nails, but the evidence is weak. High doses can interfere with lab tests, including thyroid tests and troponin (a heart attack test), so tell your doctor if you take it.
• Iron: helps only if you are iron deficient. Get tested first, because excess iron is harmful.

Treating the cause

Thyroid treatment, iron replacement, antifungal medicine or treatment of psoriasis or lichen planus improves the nails as they grow out.

Frequently asked questions

What deficiency causes brittle nails?

Iron deficiency is the best-established nutritional cause of brittle nails and spoon-shaped nails. Low zinc, protein or overall malnutrition may contribute. Most people with brittle nails have no deficiency. Their nails are damaged by water, chemicals and aging.

Why are my nails suddenly brittle?

Sudden brittleness usually follows a change in routine: more handwashing, new cleaning products, gel manicures, cold dry weather or a new medicine. If it comes with tiredness, weight change, hair loss or other symptoms, ask a doctor to check iron and thyroid levels.

Does biotin help brittle nails?

Biotin may strengthen nails in some people, but the evidence comes from small studies. It is generally safe, but high doses can give falsely high or low results on some blood tests, including thyroid and heart tests, so tell your doctor you take it.

How long does it take to fix brittle nails?

Damaged nail does not repair itself. You need to grow healthy new nail, which takes about 4 to 6 months for a fingernail and up to 18 months for a big toenail. Consistent moisturizing and protection make the new growth stronger.

Can brittle nails be a sign of thyroid problems?

Yes. An underactive thyroid often causes dry, brittle, slow-growing nails along with dry skin, hair thinning, tiredness and feeling cold. An overactive thyroid can cause nails to lift from the nail bed. A simple blood test can check thyroid function.