The Bottom Line

Brittle, splitting, or peeling nails are extremely common — estimated to affect about 20% of the population, with women affected more often than men. The most frequent cause is not a vitamin deficiency, but rather repeated wetting and drying of the nails. The key to improvement is protecting the nail from moisture fluctuations and avoiding harsh chemicals. Most people see meaningful improvement within 3–6 months with consistent care. If brittle nails do not improve or are accompanied by other symptoms, a dermatologist can check for an underlying thyroid problem, iron deficiency, or other internal cause.

What Is Onychorrhexis?

Onychorrhexis is the medical term for brittle nails — nails that crack, peel, split, or break easily. It refers to a specific type of nail fragility where the nail develops longitudinal ridges (lines running from the base to the tip) and splits along those lines. This is distinct from onychoschisis, where the nail layers separate horizontally, causing the tip of the nail to peel apart in layers. In practice, many people experience both types of brittleness together.

What Does It Look Like?

  • Nails that break easily, especially at the tip
  • Nails that peel apart at the tip in thin horizontal layers (onychoschisis)
  • Vertical ridges running from the base to the tip of the nail
  • Nails that crack lengthwise (onychorrhexis proper)
  • Nails that appear dull rather than shiny
  • Nails that seem thinner or more flimsy than they used to be

Brittle nails primarily affect fingernails — toenails are less commonly affected because they are less frequently exposed to water and chemicals.

What Causes Brittle Nails?

Repeated Wet-Dry Cycles (Most Common)

The most common cause of brittle nails is external — repeated exposure to water followed by drying. When nails get wet, they expand. When they dry, they contract. This repeated expansion and contraction weakens the nail plate over time, causing the layers to separate. People who wash dishes frequently, work in healthcare, work as hairdressers or bartenders, or swim regularly are particularly prone to this type of brittle nails.

Harsh Chemicals

Nail polish removers containing acetone, household cleaning products, and other harsh chemicals strip moisture and lipids from the nail plate. Acetone-based removers are especially drying. Even nail polish itself, if worn continuously without breaks, can cause brittleness through the solvents in the polish and the removal process.

Aging

Nails naturally become more brittle with age. After 60, approximately 20% of women and a significant proportion of men have notable nail fragility. The nail plate thins and loses water content more easily as we age.

Thyroid Disease

Both hypothyroidism (underactive thyroid) and hyperthyroidism (overactive thyroid) can cause brittle, fragile nails. If you have other symptoms — fatigue, weight changes, hair loss, temperature sensitivity — a thyroid blood test is worth requesting.

Iron Deficiency Anemia

Low iron levels can cause nails to become thin, brittle, and develop a characteristic spoon-shape (koilonychia). This is more common in people with heavy menstrual periods, those who follow a vegetarian or vegan diet without iron supplementation, or those with chronic blood loss.

Biotin: What the Evidence Actually Says

Biotin (vitamin B7) supplements are widely marketed for brittle nails. The evidence is limited but somewhat supportive — small clinical trials have shown modest improvement in nail thickness and reduced brittleness with biotin 2.5 mg daily. Biotin deficiency itself is rare, but supplementation even in people without frank deficiency appears to help some individuals. It is generally safe and worth a trial, but expect to take it for 3–6 months before judging effectiveness. Note that biotin can interfere with certain laboratory tests (thyroid tests, troponin tests), so tell your doctor if you take it.

Treatment and Care: What Actually Works

Moisture Management (Most Important Step)

  • After washing hands, apply a hand cream or cuticle oil immediately while hands are still slightly damp — this seals moisture in
  • Use a thick cream (not a watery lotion) at night and wear cotton gloves while sleeping
  • Apply cuticle oil (jojoba, coconut, or vitamin E oil) to the base of the nail and nail edges daily
  • Wear rubber gloves lined with cotton when washing dishes or using household cleaners

Protective Nail Habits

  • Keep nails trimmed short — shorter nails break less and are exposed to fewer wet-dry cycles at the tip
  • File nails with a fine-grit nail file in one direction; back-and-forth sawing weakens the free edge
  • Use nail polish remover that is acetone-free, and limit removals to every 2 weeks or less
  • Consider wearing a nail hardener or a base coat to provide mechanical protection
  • Avoid using nails as tools to open packages or pry lids

Medical Treatments

For brittle nails that do not respond to the above measures, a dermatologist may recommend:

  • Biotin 2.5 mg daily (if not already tried)
  • Evaluation and treatment of an underlying cause (thyroid disease, iron deficiency, lichen planus)
  • Prescription urea-based nail preparations to improve hydration

When to See a Dermatologist

  • Brittle nails that do not improve after 3–6 months of consistent at-home care
  • Nails that are thinning, spoon-shaped, or have unusual color changes alongside brittleness
  • You have other symptoms that might suggest thyroid disease, anemia, or another internal condition
  • Only one or a few nails are brittle rather than all nails (asymmetric involvement may suggest fungal infection or nail psoriasis)
  • A nail is painful, swollen, or has changed color significantly

Frequently Asked Questions

Is biotin worth taking for brittle nails?

It is worth trying — it is safe and may help. Take 2.5 mg daily and give it at least 3–4 months. Just remember to tell any doctor ordering blood tests that you are taking biotin, as it can falsely skew thyroid and cardiac test results.

Will cutting my nails shorter actually help?

Yes. Shorter nails have less free edge to catch and break. Shorter nails are also exposed to fewer wet-dry cycles at the tip. Once shorter nails feel stronger, you can gradually grow them longer.

Could my brittle nails be a sign of something serious?

Most brittle nails come from external factors (water, chemicals). But if brittleness appeared suddenly, all nails are affected, or you have other symptoms like fatigue, hair loss, or cold intolerance, it is worth checking thyroid function and iron/ferritin levels.

Are gel nails or acrylics bad for brittle nails?

Gel and acrylic overlays can protect brittle nails in the short term, but the application and removal process — especially repeated filing and acetone soaking — damages the nail plate and can make brittleness worse long-term. Take regular breaks to let nails recover.

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  3. Colombo VE, et al. Treatment of brittle fingernails and onychoschizia with biotin. J Am Acad Dermatol. 1990;23(6 Pt 1):1127-1132.
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Trusted Resources

Always consult a board-certified dermatologist for diagnosis and personalized treatment recommendations. This article is for educational purposes only.