Why do my nails peel and split?

Two different failures

Peeling — the nail separates into flaky layers at the free edge, like plywood coming apart. The clinical term is onychoschizia, and it is a delamination problem.

Splitting — a crack runs down the nail, usually starting at the free edge and traveling toward the cuticle. This is a fracture problem.

They look similar in a photo and they are not the same. Peeling is usually about water and chemical exposure; splitting is usually about trauma, dryness or catching the nail on something.

What causes peeling

Repeated wetting and drying. This is the big one. The nail plate absorbs water and swells, then dries and contracts, and the layers work apart over many cycles. The AAD is direct: too much water exposure can weaken your nails, causing them to split, peel or break, and recommends wearing gloves for cleaning and washing dishes.

Acetone and harsh removers. Repeated acetone strips oil out of the plate. Layers without oil between them separate more easily.

Aggressive filing. Sawing at the free edge with a coarse board separates the layers mechanically. A fine glass file cuts cleanly instead — this single change fixes more peeling than any product does.

Enhancement removal. Peeling a gel or press-on tip off takes the top layer of the plate with it, and what is left delaminates from there. See repairing nails after gel.

What causes splitting

Dryness. A dry nail is a rigid nail, and a rigid nail fractures instead of flexing. This is why oil helps splitting even though oil sounds like the wrong tool for a crack.

Length. Length is leverage. The same knock that a short nail absorbs will crack a long one.

Using nails as tools. The AAD lists this among its healthy-nail basics for a reason — opening cans and prising things apart is how a great many splits start.

A snag that was not filed. A rough edge catches, and a catch tears further than a file would have taken. The AAD recommends keeping nails shaped and free of snags by filing.

What actually helps, for both

Note the last row. A protein or hardening treatment helps soft, peeling nails and makes brittle, splitting nails worse by making them more rigid. This is the most common mistake in the whole category — see nail strengtheners.

How long before it improves

Changes you make today affect the nail you grow, not the nail you have. The AAD puts full fingernail replacement at around six months, so:

• Days: the existing nail becomes more flexible with daily oil, and stops catching once you file the snags off.
• Weeks: new growth at the base looks better than the older nail ahead of it, and you can see the difference as a line.
• Months: the improved nail reaches the free edge and the peeling stops recurring.

Most people give up in week three because the free edge still peels. The free edge is old nail. It was always going to.

When it is not a nail care problem

Peeling and splitting are usually mechanical and usually fixable with the changes above. Some nail changes are not, and it is worth knowing the difference.

The AAD advises seeing a board-certified dermatologist if nails change, swell or cause pain, and notes that people with diabetes or poor circulation should be particularly attentive. Specifically worth a professional look: nails that change color, thicken noticeably, separate from the nail bed, develop dark streaks, or hurt.

A bottle of strengthener is not the answer to any of those, and a delay in identifying them is not free.