Brittle nails: why they snap, and the routine that helps

A brittle nail is a dry nail. Keratin bends when it has enough water and oil between its layers, and it cracks when it has too little. The same nail that snaps in January, after weeks of hand washing and central heating, often behaves itself in June. That pattern points to a cause on the outside.

Dermatologists group brittle nails into two kinds. Soft, thin nails that peel at the tip are the water-logged kind, seen in people who wash their hands often or work with wet hands. Hard, dry nails that crack lengthwise are the dehydrated kind, common with age and heavy solvent use. Both respond to the same routine, and both have a short list of medical causes to rule out when care alone fails.

What causes brittle nails?

The NHS lists ageing, long contact with water or chemicals, injury, nail biting and fungal infection as the common causes of nails that break easily, and names iron deficiency anaemia and thyroid disorders among the conditions that change nails¹. The American Academy of Dermatology (AAD) is specific about water: too much exposure weakens nails and makes them split, peel or break².

The MSD Manual notes that with ageing nails become dry and brittle and may split, and that they can flatten and develop lengthwise ridges⁴. More oil and shorter nails offset most of that effect.

Why does water make nails brittle?

The nail plate is porous. It takes up water within minutes, swells, and then loses that water as the hand dries. Each cycle stretches and relaxes the bonds between the flat keratin cells that make up the plate. Twenty cycles a day, with detergent in the water, loosen the layers until the tip peels and the edge cracks.

This is why the AAD's list of tips puts water first: keep nails clean and dry, wear gloves when cleaning or washing dishes, and moisturise after hand washing. The Mayo Clinic gives the same advice, with the addition of a hand lotion rubbed into the nails and cuticles each time³. A long soak before a manicure is the same problem in miniature: the plate swells, polish goes on, the plate shrinks, the polish chips.

Remover is water's partner. Acetone dissolves polish fast, and used for a short time it is the least traumatic option because it needs the least rubbing, but prolonged soaking dries the plate and leaves white, flaky patches⁷. The choice between removers is set out in acetone vs acetone-free remover; the fuller account of water damage is in nails, water and household cleaning.

Can iron deficiency or thyroid problems cause brittle nails?

Yes, and they are the two tests worth asking for when nails stay brittle after three months of good care. Iron deficiency can make nails thin and brittle and, when it is marked, spoon-shaped, with edges that turn up; the NHS and the AAD both list spoon nails as a sign of low iron. The Cleveland Clinic links iron deficiency to vertical ridges and spoon nails and thyroid disease to dry, ridged, brittle plates⁵.

The pattern helps tell an internal cause from an external one. Water and solvent damage is worst on the hand you use most, and it improves with gloves. An internal cause affects all ten nails at about the same time, often with other signs: tiredness, hair shedding, dry skin, feeling cold, or heavy periods. A GP can check a full blood count, ferritin and thyroid function from one sample. Deficiencies of zinc, protein and some B vitamins are rarer causes, covered in nails and diet.

What is the oil-and-glove routine?

The routine has two halves. Gloves cut the number of wet-and-dry cycles; oil replaces what the remaining cycles remove. Dermatologists quoted by WebMD on onychorrhexis (nails that split lengthwise) give the same two instructions: wear gloves while cleaning or washing dishes, and use a lotion or oil on the hands, nails and cuticles⁶.

You will need

• Cotton-lined rubber gloves for washing up and cleaning
• A cuticle oil with jojoba, sweet almond or a similar plant oil (India Anaïs Gold Drop is one example; sold out, with the next edition planned for spring 2027)
• A hand cream to seal the oil in
• A fine file, 240 grit or a glass file
• A thick occlusive balm for nights when the cuticles crack

The daily routine

1. Put the gloves on for every wet task longer than a minute, and dry your hands fully afterwards.
2. After each hand wash, rub a little hand cream into the nails and the skin around them.
3. Morning and night, massage one drop of oil into each nail and cuticle. Oil can go over polish.
4. Keep nails short while they are weak. A short nail has less leverage and snaps less.
5. Once a week, file the free edge in one direction only, with a slightly rounded shape.
6. Remove polish with the shortest solvent contact you can manage, then oil straight away.
7. On cold or dry nights, put a thick balm over the oil and sleep in cotton gloves.

The plate being made now reaches the tip in three to six months, so the routine needs one growth cycle before you judge it. Which oils suit nails and why are covered in cuticle oil: ingredients and how to use it, and the cream step in hand cream and your nails.

Do nail hardeners and biotin help brittle nails?

Nail hardeners are films that cross-link keratin, most often with formaldehyde or a related molecule. They make the plate stiffer, which stops a soft nail from bending and tearing. Used every day for weeks, the same cross-linking removes moisture and makes the nail overly hard and brittle in its own way, according to the technical explanation on Salon Geek. A hardener suits soft, peeling nails for a few weeks, paired with oil, and makes dry, cracking nails worse.

Biotin is the supplement most often suggested. The Mayo Clinic advises asking a healthcare provider whether biotin might help weak or brittle nails; the evidence is small and old, and biotin supplements can interfere with some laboratory tests, including thyroid tests. That matters here, because thyroid function is one of the tests a GP may run for brittle nails. The studies and the caveats are in biotin for nails: what the evidence says.

When should you see a GP about brittle nails?

Brittle nails on their own rarely need a doctor. The AAD advises seeing a dermatologist when nails change, swell or cause pain, and sooner for anyone with diabetes or poor circulation. The NHS advises a GP visit when a nail changes shape or colour without a reason you know, or when the skin around it becomes sore, red, swollen and warm.

• All ten nails have become brittle over a few months, with tiredness, hair loss, dry skin or feeling cold.
• Nails are turning up at the edges (spoon nails).
• A nail is thick, crumbly or yellow, which points to a fungal infection.
• Three months of gloves and daily oil have made no difference.
• A nail is lifting from its bed, or there is a new dark line under it.

The last point is unrelated to brittleness and should never wait. The full list of changes that need a medical opinion is in nail changes: when to see a doctor, and the wider routine is in the nail care guide.

Written and fact-checked by the India Anaïs editorial team. Every number and rule is linked to its source. How the guides are made.