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Medically reviewed guide · Last updated: 23 July 2026 · Reading time: approx. 9 min.
Brittle nails: causes and what helps
At a glance
What is it?Nails that split, peel off in layers or tear easily — medically known as onychoschisis or onychorrhexis
Usually harmless?Yes — external strain is usually behind it; only rarely a condition that needs treatment
Common triggersFrequent wetness, nail polish remover, cold, ageing — less often iron deficiency or the thyroid
Warning signsBrittle nails plus fatigue or hair loss, or discoloured, thickened nails
Key distinctionJust brittle, or also discoloured and thickened? The latter points more towards nail fungus
What to do?Protect and care for the nails; have your blood values checked if other symptoms occur
Keep an eye on nail changes
Record changes, accompanying symptoms and your values in brite — a clear overview that is worth its weight in gold at your doctor's appointment. Free of charge.
Nails are described as brittle when they lose their firmness and easily split, tear or peel off in thin layers at the free edge. Experts distinguish two patterns: the layered splitting at the nail tip (onychoschisis) and fine lengthwise cracks that make the nail look "frayed" (onychorrhexis). At their core both mean the same thing — the nail is not resilient enough.
The nail is made of the protein keratin, which is arranged in many thin layers stacked on top of one another. To stay elastic, it needs a certain moisture and oil content. If the nail plate dries out or is constantly irritated, the layers come apart from one another — the nail becomes brittle. The fingernails are affected particularly often, because the hands are exposed to the most water, cleaning agents and temperature changes.
The most important thing first
In the vast majority of cases, brittle nails are a matter of care and strain, not a sign of illness. The question of an internal cause only becomes important once additional symptoms appear or the colour and shape of the nails change.
2. Harmless or a warning sign?
The decisive question is not "are my nails brittle?", but "what else is going on?". Two situations should be kept apart:
Only the nails are affected: usually harmless. If only the fingernails are brittle and this can be explained by wetness, nail polish or the cold season, external strain is almost always behind it.
Brittle nails plus further symptoms: you should pay attention if fatigue, paleness, hair loss, feeling cold or weight changes also occur. This combination can point to an iron deficiency or an underactive thyroid.
The nails themselves can also give clues: ridges, discolouration, thickening or spoon-shaped, dented nails are more than just "brittle" and should be assessed by a doctor (more on this in the chapters "Nail fungus or just brittle?" and "When to see a doctor?"). Brittle nails are not a real emergency, though — there is time to look for the cause calmly.
3. Causes & triggers
With brittle nails it is worth distinguishing between external influences (which act on the nail from the outside) and internal causes (within the body). The external ones are by far the most common.
External strain — the most common cause:
Frequent wetness: constant hand washing, cleaning and washing up make the nail swell and then dry it out — the layers come apart.
Nail polish remover & chemicals: especially acetone-based removers, aggressive cleaners and frequent gel or Shellac polish strip the nail of oil and moisture.
Cold and dry heated air: in winter nails dry out particularly and become more brittle.
Mechanical irritation: manicures with filing down to the nail bed, "picking" or using the nails as a tool.
Internal causes — rarer, but important:
Iron deficiency: one of the most common internal causes; often together with fatigue, paleness and hair loss.
Thyroid function: both an under- and an overactive thyroid can change the nails.
Ageing: over the years the nail plate naturally becomes thinner and drier — brittle nails are very common in older age.
Skin conditions: such as psoriasis or eczema, which can also affect the nails.
Biotin deficiency: a genuine deficiency is rare, but it can weaken the nails (more on this below).
The connection with wet work, nail polish or the season in particular is easy to observe yourself. A simple log helps to spot patterns.
4. Nail fungus or just brittle?
The most important distinction with brittle nails is from nail fungus. Both can make the nail crumbly — but the treatment is completely different. The difference lies above all in colour and thickness: a "merely" brittle nail stays normal in colour and shape and splits at the edge. A fungal nail, by contrast, is typically discoloured (yellowish-whitish to brownish) and thickened and often crumbles away from the tip.
Feature
Just brittle
More likely nail fungus
Colour
Normal, possibly dull
Yellowish, whitish, brownish
Thickness
Normal or thinner
Often thickened
Surface
Splits, flakes at the edge
Crumbly, crumbles away
Affected
Usually several fingernails
Often single toenails, spreads
Table scrollable to the right
The nail surface itself can also reveal something: fine lengthwise ridges are mostly harmless and increase with age. Transverse ridges (so-called Beau's lines) form when nail growth was briefly disrupted — for example after a feverish infection. Spoon nails (nails curved upward and dented) can be a sign of pronounced iron deficiency. Such changes in shape should be looked at by a doctor, but are no reason to panic.
Document nail changes
With brite you record how your nails and any accompanying symptoms develop — the best basis for the practice to quickly get to the bottom of the cause.
Brittle nails are almost always harmless and not an emergency. But there are situations in which a medical assessment is worthwhile — above all because the nails can sometimes point to something else in the body.
You should have things assessed promptly if fatigue, paleness, hair loss, feeling cold or weight changes also occur, if the nails are discoloured or thickened (suspected nail fungus), if shape or colour change markedly (spoon nails, transverse ridges, dark streaks) or if the nails keep getting more brittle over months despite good care.
Not an emergency — but have it assessed by a doctor
Brittle nails alone are no reason to call the emergency number. But have them looked at by a doctor if sudden nail changes combine with further symptoms such as fatigue or hair loss, or if you notice suspicious dark streaks, discolouration or thickening. A newly appeared dark lengthwise streak in the nail should be assessed by a dermatologist.
6. Diagnosis
To find the cause, the practice often needs only a close look and a few examinations. It is important to describe accompanying symptoms and the course over time.
Iron and ferritin levels, blood count, thyroid values
Nail sample (if fungus suspected)
Detection of fungi by swab or culture
Dermatological assessment
Distinction from psoriasis, eczema or other nail conditions
Table scrollable to the right
Because nails grow only slowly, the success of a treatment only shows after weeks to months. A fingernail takes around half a year and a toenail up to a year to grow back completely. So a little patience is part of it.
7. What you can do yourself
Protect the nails from water and chemicals: wear gloves when cleaning and washing up and limit wet work.
Restore oils: regularly apply a rich cream or a nail oil to nails and cuticles — ideally after every hand wash.
Care gently: file rather than cut the nails, in one direction, and avoid acetone-based removers as well as permanent gel/Shellac polish.
Eat a balanced diet: a varied diet with protein, iron and zinc supports healthy nails; make up any proven deficiency specifically.
Put biotin in realistic perspective: supplements only help noticeably with an actual deficiency — with a balanced diet the benefit is uncertain (more on this below).
Keep a log: note down when the nails get worse and what you observe — this helps you and the practice.
Spot triggers, understand patterns
brite helps you document the state of your nails and possible triggers over time — free of charge and ad-free.
Nails change slowly — and that is exactly what makes it hard to gauge cause and progress. Anyone who records changes, accompanying symptoms and values over time gives the practice the decisive clues. brite makes that easy.
Health timeline — document the state of the nails, accompanying symptoms (fatigue, hair loss) and possible triggers over time and bring it along as an overview to your appointment. Track your timeline
Intake reminder — if iron, biotin or an antifungal nail lacquer is prescribed, brite reliably reminds you to apply it regularly over the many weeks until success. Set up a reminder
Interaction check — checks whether your preparations are compatible; for example, the body absorbs iron less well if it is taken at the same time as certain agents. Check now
Digital medication plan — all preparations and dietary supplements clearly in one place for your GP and dermatologist. To the medication plan
Usually not. In the vast majority of cases, external strains such as frequent wetness, nail polish remover or cold are behind it. A nutrient deficiency — above all iron — is rarer and often shows up together with further symptoms such as fatigue, paleness or hair loss. In that case a blood test is sensible.
Only to a limited extent. A genuine biotin deficiency is rare; if present, biotin can strengthen the nails. With a balanced diet and no deficiency, the benefit of taking biotin is not scientifically proven for certain. High biotin doses can also distort laboratory values — so discuss taking it with your practice.
The most important difference is colour and thickness. A merely brittle nail stays normally coloured and splits at the edge. A fungal nail is typically discoloured yellowish-whitish to brownish, thickened and crumbles away. Nail fungus often affects single toenails and spreads. If suspected, a nail sample can provide clarity.
Fine lengthwise ridges are mostly harmless and increase with age. Transverse ridges form when nail growth was temporarily disrupted, for example after a feverish infection. Spoon nails — nails curved upward and dented — can be a sign of pronounced iron deficiency and should be looked at by a doctor.
Cold and dry heated air draw moisture out of the nail, which makes it more brittle. In addition, people often wash their hands more frequently in winter. Regularly moisturising nails and cuticles as well as wearing gloves for wet work and in the cold help keep the nails elastic.
Yes. Both an underactive and an overactive thyroid can change the nails and make them brittle. If further signs such as fatigue, feeling cold, weight changes or hair loss occur, a blood test of the thyroid values is part of the assessment.
Patience is needed. Nails grow slowly: a fingernail takes around half a year and a toenail up to a year to grow back completely. The success of care or a treatment therefore only shows after weeks to months on the newly regrowing nail.
The most effective thing is to protect the nails from water and chemicals and to restore their oils regularly. Wear gloves for wet work, apply a nail oil or a rich cream to nails and cuticles after washing your hands, file rather than cut, and avoid acetone-based removers as well as permanent gel polish.
Have the nails assessed if fatigue, paleness or hair loss also occur, if the nails are discoloured or thickened, if shape or colour change markedly (spoon nails, dark streaks) or if they keep getting more brittle over months despite good care. A new dark lengthwise streak should be assessed by a dermatologist.
German Dermatological Society (DDG): Nail conditions and nail care. derma.de
German Nutrition Society (DGE): Biotin and nail health. dge.de
This article is for general information and does not replace medical advice, diagnosis or treatment. Brittle nails are not an emergency — but if sudden nail changes occur together with further symptoms such as fatigue or hair loss, or if you notice suspicious discolouration, thickening or dark streaks, please have this assessed by a doctor.
