Brittle nails: causes and remedies to strengthen them

Brittle nails that break easily or peel into layers affect up to 20% of the population. The most common causes are external: water, detergents, chemicals, and repeated minor trauma. The most effective remedies are consistent care and a little patience, because a fingernail takes about six months to renew itself; some signs, such as a dark band or a change in nail color, require a dermatologist.

In this guide, learn why nails weaken, when to be concerned, how to protect your nails every day, and what studies say about nutrition and supplements.

Reading time: 9 minutes

Last updated: October 2026

Scientific review: GP Nutraceuticals Team

Main sources: International review of brittle nails (Dermatology and Therapy 2020), clinical studies on vitamins, keratin, collagen, and silicon

What do brittle nails indicate?

Nails are made of keratin, the same protein as hair, arranged in compact layers held together by lipids and water: this nail structure determines nail strength. When hydration and cohesion between the layers are disrupted, the nail splits into layers, breaks at the edge, or develops longitudinal grooves.

Brittle nails are more common in women and in people over 50, when the nail plate tends to dry out and thin nails are more common. In most cases, it is an "idiopathic" condition, meaning there is no underlying disease; more rarely, it signals a nutritional deficiency or a condition that needs to be identified.

Brittle nails: 5 key points

The guide's key message in five points: the condition is common, mostly due to external factors, and improves with consistent care.

• Brittle nails affect up to 20% of the population, especially women over 50.
• Water, detergents, solvents, and repeated trauma are the most common causes.
• A dark band, changes in color or shape, and nail separation require a dermatologist.
• Gloves, moisturizer, and short nails are the first line of treatment.
• A fingernail takes about six months to renew itself: any treatment takes time.

What you'll find in this guide

This guide starts with nail structure and growth, moves on to the causes of brittleness and warning signs, and ends with daily care, nutrition, studied nutrients, and frequently asked questions.

• Nail structure and growth.
• Causes of weakened nails.
• When to see a dermatologist and which tests to get.
• Daily care and nutrition for stronger nails.
• What studies say about vitamins and other nutrients.
• Frequently asked questions.

This guide is for informational and educational purposes only and does not replace advice from a doctor or other qualified healthcare professional.

Nail structure and growth: how do nails grow?

The nail grows from the matrix, an area of cells hidden beneath the cuticle that continuously produces keratin. New cells push older ones forward, where they flatten and form the nail plate we see.

According to a study of healthy young adults, fingernails grow an average of 3.5 mm per month, while toenails grow about 1.6 mm. A fingernail therefore takes about six months to renew completely, while the big toenail takes over a year. That's why any change, in care or diet, takes months to become visible: the new nail has to grow to the edge.

Why do nails break and peel? Causes of brittle nails

Brittleness occurs in two main forms: onychoschizia, which is horizontal splitting at the free edge, and onychorrhexis, with longitudinal grooves and cracks. The two often occur together, making the nail appear thin, dull, and inelastic.

Main causes: water, cleansers, and trauma

In most cases, external factors can weaken nails by affecting the nail plate's moisture and cohesion:

• hands that are often wet, alternating between wetting and drying, harsh cleansers;
• solvents and acetone, semi-permanent nail polish, artificial nails, and repeated nail enhancements;
• repeated minor trauma, such as using your nails as tools or typing for a long time with long nails, or the habit of biting your nails;
• age, because the nail plate becomes drier and thinner over time.

What conditions can make nails weak and brittle?

Less commonly, brittle nails can signal a health problem: iron deficiency, thyroid disorders, diseases affecting the skin and nails, such as psoriasis and lichen planus, fungal infections (onychomycosis), or a nutritional deficiency linked to very restrictive diets. In these cases, nail care alone isn't enough: work with your doctor to identify any underlying causes.

Very brittle nails: when to see a dermatologist and what tests to have?

If your nails remain brittle despite a few months of consistent care, or if changes other than simple brittleness appear, it's a good idea to have them checked by a dermatologist. Some signs warrant a visit without waiting:

• a recently appeared longitudinal dark band, especially if it widens or involves the surrounding skin;
• nails that change color, thicken, or separate from the nail bed;
• tiny, pinpoint depressions on the surface, typical of psoriasis;
• spoon-shaped, concave nails, which may indicate iron deficiency;
• redness, swelling, or pain around the nail.

To identify the cause, a dermatologist may request a fungal test if they suspect a fungal infection, and blood tests such as a complete blood count, ferritin, and TSH to rule out iron deficiency and thyroid disorders, then recommend targeted treatment for your nails.

How can you strengthen brittle nails and get them back to normal?

The best nail care is also the simplest: take care of your nails every day by protecting the nail plate from water, detergents, and the chemicals in nail polish removers, and keeping your nails hydrated. That is how they return to normal: but strong, beautiful nails take a few months and a little consistency, while the new nail grows in.

What natural remedies make nails stronger?

The most helpful remedies are simple habits that protect the nail plate and keep it hydrated: this is the best way to improve nail strength from the outside.

• Wear gloves when washing dishes and cleaning: it is the simplest way to protect your nails.
• Apply moisturizer to your hands, nails, and cuticles every day, especially after washing them.
• Choose acetone-free removers and take breaks between gel manicures.
• Keep your nails short and file them in one direction with a fine-grit file.
• Do not cut or forcefully push back your cuticles, which protect the nail matrix.
• In the evening, massage your nails and cuticles with a few drops of vegetable oil (such as almond or jojoba oil) or petroleum jelly, which help retain water in the nail plate.

What should you eat to have strong, healthy nails?

To keep nails healthy, a varied diet provides the building blocks for producing keratin: high-quality protein (fish, eggs, meat, dairy, legumes), iron (meat, legumes, leafy green vegetables), zinc (seafood, seeds, whole grains), and vitamins and minerals from fruit and vegetables. Very restrictive diets, on the other hand, can compromise nail health; like hair, nails are quick to show the effects of a deficiency.

Dietary supplements to strengthen brittle nails: what do studies say?

Biotin, keratin, collagen, and silica have been studied most often for brittle nails. The results are promising, but they are based on few studies, often small and without a control group. A 2020 international review suggests that vitamins, trace elements, and amino acids, particularly cysteine, may help, along with topical care.

Scientific evidence and regulatory claims are two different things. An authorized label claim describes a physiological function recognized by an authority; it does not prove that a product can treat brittle nails. Likewise, a positive study alone does not authorize a claim.

Vitamins, keratin, and other nutrients for nails: what studies suggest

Which claims are permitted for nails?

Regulation (EU) 432/2012 provides for specific claims for nails for only two minerals:

• Zinc contributes to the maintenance of normal nails;
• Selenium contributes to the maintenance of normal nails.

Biotin has authorized claims for hair and skin, but not for nails. There are no authorized claims for nails for keratin, collagen, cystine, or silicon.

Frequently asked questions about brittle nails

Brief answers to the most common questions about the causes, care, and products for splitting nails.

Why do nails split, and what causes it?

Mainly because of alternating between getting wet and drying, which causes the nail plate to swell and then contract, and because detergents and solvents strip away its lipids. The layers of keratin lose cohesion and separate at the free edge.

Do white spots on nails indicate a calcium deficiency?

No, that’s a myth. Small white spots are almost always a sign of microtrauma at the base of the nail and disappear as it grows. Calcium plays only a minor role in nail hardness.

Do semi-permanent nail polish and artificial nails damage nails?

Removal in particular, which requires filing and solvents, can damage nails; the same applies to gel and nail enhancements, which thin the nail plate. It’s best to rely on experienced professionals, avoid forcibly peeling them off, and give your nails a few weeks’ break between applications: the break isn’t needed to let nails breathe, since they get oxygen from the blood, but to let them rest from filing and solvents.

Which products work to strengthen nails?

Among nail care products, hand and cuticle creams and oils are the basics because they keep the nail plate moisturized. Nail-strengthening polishes containing hydroxypropyl chitosan, applied like clear nail polish, have shown encouraging results in some clinical studies. However, it is best to avoid prolonged use of formaldehyde-based hardeners, which can stiffen the nail plate, make it more brittle, and cause allergies.

How long does it take to strengthen nails?

Nails can improve only as they grow: fingernails need at least 4-6 months, the time it takes for a new nail to replace the brittle one. Toenails take over a year.

Can the thyroid affect nail health?

Yes, thyroid disorders can contribute to brittle nails and are among the possible internal causes, along with iron deficiency. If brittleness is accompanied by fatigue, hair loss, or other symptoms, it is useful to discuss this with your doctor and have blood tests.

Which vitamin is lacking when nails break?

Usually none: in most cases, brittleness is due to external factors, not a deficiency. Among deficiencies, iron deficiency is the most common, while biotin deficiency is rare. Some small studies without a control group observed harder nails with 2.5 mg a day of this vitamin, but placebo-controlled studies are lacking; high doses can also distort some laboratory test results.

In summary

Brittle nails are a common problem, mainly caused by water, detergents, solvents, and minor injuries. Gloves, daily moisturizing cream, keeping nails short, and taking breaks from semi-permanent nail polish are the first steps in nail care, with visible results after a few months.

Studied nutrients such as keratin, silicon, and collagen have shown encouraging results in small studies. However, a dark band, changes in color or shape, or persistent brittleness require assessment by a dermatologist.

The GP Nutraceuticals nutraceutical approach

A supplement does not replace daily nail care or a dermatologist's assessment when needed. However, it can complement a balanced diet with nutrients that contribute to the maintenance of normal nails.

RevePil Forte® is a dietary supplement in sachets that combines zinc, selenium, biotin, copper, vitamin C, vitamins B6 and B12, and pantothenic acid with sulfur-containing amino acids (L-cystine and L-methionine), keratin, hydrolyzed collagen, and extracts of Annurca apple and millet. Take one sachet a day for courses lasting at least three months.

Among the authorized claims for its ingredients:

• zinc and selenium contribute to the maintenance of normal nails;
• biotin, zinc, and selenium contribute to the maintenance of normal hair;
• vitamin C contributes to normal collagen formation for the normal function of the skin;
• vitamin B6 contributes to normal cysteine synthesis.

During pregnancy and breastfeeding, do not take the product without first consulting your doctor. Before having blood tests, inform your doctor that you are taking it, as high doses of biotin may interfere with some tests.

Sources and scientific references

This guide was prepared based on peer-reviewed scientific literature and institutional sources available at the time of the update.

Brittle nails: causes and growth

1. Chessa MA, Iorizzo M, Richert B, et al. Pathogenesis, clinical signs and treatment recommendations in brittle nails: a review. Dermatol Ther (Heidelb). 2020. PMID: 31749091
2. Yaemsiri S, Hou N, Slining MM, He K. Growth rate of human fingernails and toenails in healthy American young adults. J Eur Acad Dermatol Venereol. 2010;24(4):420-423. PMID: 19744178

Nutrients and supplements

3. Floersheim GL. Treatment of brittle fingernails with biotin. Z Hautkr. 1989. PMID: 2648686
4. Colombo VE, Gerber F, Bronhofer M, Floersheim GL. Treatment of brittle fingernails and onychoschizia with biotin: scanning electron microscopy. J Am Acad Dermatol. 1990. PMID: 2273113
5. Hochman LG, Scher RK, Meyerson MS. Brittle nails: response to daily biotin supplementation. Cutis. 1993. PMID: 8477615
6. Beer C, Wood S, Veghte RH. A clinical trial to investigate the effect of Cynatine HNS on hair and nail parameters. ScientificWorldJournal. 2014. PMID: 25386609
7. Barel A, Calomme M, Timchenko A, et al. Effect of oral intake of choline-stabilized orthosilicic acid on skin, nails and hair in women with photodamaged skin. Arch Dermatol Res. 2005. PMID: 16205932
8. Hexsel D, Zague V, Schunck M, et al. Oral supplementation with specific bioactive collagen peptides improves nail growth and reduces symptoms of brittle nails. J Cosmet Dermatol. 2017. PMID: 28786550

Institutional and regulatory sources

9. U.S. Food and Drug Administration. Biotin (Vitamin B7): Safety Communication – May Interfere with Lab Tests. 2017. fda.gov
10. Commission Regulation (EU) No 432/2012, establishing a list of permitted health claims made on foods. eur-lex.europa.eu

Update history

We update this guide when new guidelines or relevant studies are published.

Version 1.0 – October 2026

First published. Main sources: international review on brittle nails (2020) and clinical studies on biotin, keratin, silicon, and collagen peptides.