Wavy Nails: Causes of Vertical and Horizontal Ridges and Toenail Ridging, and Whether They Are Dangerous, Explained by a Dermatologist

3 days ago

12 min read

Wavy nails means the nail surface is uneven, with ridges or grooves running across the nail. Most often this is a harmless change that comes with age, but some patterns are a sign of a skin condition or a problem elsewhere in the body that should be examined.

The key to telling them apart is the direction of the ridges. Vertical ridges (running from the base of the nail to the tip) and horizontal ridges (running across the nail) have completely different causes, and toenails have their own set of causes that differ from fingernails.

In this article, a dermatologist walks through each pattern, answers the popular question "Which vitamin deficiency causes wavy nails?" directly, and teaches a technique doctors actually use: working backwards to estimate when a horizontal groove was caused.

How many types of wavy nails are there? A comparison of vertical and horizontal ridges

Before deciding what is causing your wavy nails, look at the "direction" of the ridges and compare it with this table.

What you see	Vertical / horizontal	Common causes	Is it dangerous?
Many shallow lines from the base to the tip of the nail, seen on every finger	Vertical (Longitudinal ridging / Onychorrhexis)	Increasing age, dry nails lacking moisture	Not dangerous, no treatment needed
A single deep vertical line, a thin and fragile nail, scar tissue over the nail base	Vertical	Nail lichen planus	See a doctor, as it can permanently damage the nail
A single brown or black vertical band	Vertical (Melanonychia)	Pigment build-up, a mole under the nail, or subungual melanoma	Every case needs to be examined by a doctor
A deep groove across the nail, at the same position on several fingers	Horizontal (Beau's lines)	High fever, severe illness, chemotherapy, hand-foot-and-mouth disease	The groove itself is not dangerous, but the cause must be found
A horizontal groove on one finger only	Horizontal	Injury to the base of that nail, such as a slammed door or aggressive manicuring	Not dangerous, grows out on its own
A thick, yellow, rough toenail with irregular waves	Mainly seen on toenails	Nail fungus (Onychomycosis) or repeated pressure from shoes	Fungus should be confirmed by testing before treatment
A rough, wavy nail surface together with tiny pits	Either direction	Nail psoriasis, patchy hair loss (alopecia areata), eczema	See a doctor to treat the underlying condition

A simple rule: vertical ridges on every finger are usually part of ageing and harmless, whereas horizontal ridges, or a change affecting just one finger, are the ones that deserve attention and further examination.

What causes vertical ridges in the nails? (Longitudinal ridging / Onychorrhexis)

Vertical ridges running from the nail base to the tip are the most common type and usually not a disease. They can be compared to "wrinkles of the nail" that gradually become more visible with age, because the cells at the nail base (nail matrix) produce the nail less evenly than before.

The group you do not need to worry about can be recognised by

Many shallow parallel lines spread evenly across the nail
A similar pattern on several or all fingers
The nail does not change colour and is not painful, and does not lift or fall off
The ridges become more visible slowly with age and did not appear within a few weeks

This group is linked to dry nails, for example from frequent hand washing or contact with detergents, or long periods in an air-conditioned room. It generally does not need medication and is not a sign of serious disease.

However, some vertical ridges need further examination, including

Nail lichen planus — deep vertical lines together with a thinning, splitting nail or scar tissue over the nail base (pterygium). This group should see a doctor soon, because the nail can be permanently damaged if left untreated.
Injury to the nail base — for example a cyst pressing on the nail base, causing a single deep vertical groove on one finger that stays permanently.
A single brown or black vertical band (Melanonychia) — this is not a ridge but a band of colour and is a completely separate matter. Every case must be examined by a doctor to rule out subungual melanoma. Read more in our article on black nails.

What causes horizontal ridges in the nails? (Beau's lines)

A deep groove across the nail is called Beau's lines, which is completely different from vertical ridges. The groove forms when nail production at the nail base pauses temporarily and then restarts, leaving a mark on the nail plate as a record.

Put simply, Beau's lines are not a nail disease but a record of an event that affected the whole body. Common causes include:

High fever or severe illness such as bloodstream infection, pneumonia or major surgery
Chemotherapy, which directly suppresses cell division at the nail base. It usually appears on several fingers at once and repeats with each treatment cycle.
Hand-foot-and-mouth disease — common in children. The groove usually appears about 1-2 months after recovery, and in some cases the whole nail falls off (onychomadesis), which is a Beau's line deep enough to cut through.
Injury to the nail base such as a slammed door or aggressively pushing back the cuticle — this is usually on one finger only.
Severe malnutrition or systemic disease such as kidney failure or poorly controlled diabetes

The deciding clue: a horizontal groove at the same position on several fingers at the same time = an event that affected the whole body, while a groove on just one finger = a local injury to that finger.

Most Beau's lines grow out on their own as the nail lengthens and need no treatment of the nail itself, but if they keep recurring for no known reason you should see a doctor to look for an underlying cause.

A doctor's technique: working backwards to estimate when a horizontal groove was caused

This is the most useful part of Beau's lines and something most people do not know, because nails grow at a fairly constant rate, the distance from the nail base to the groove tells you when the event happened.

Approximate nail growth rates

Fingernails grow about 0.1 mm per day or roughly 3 mm per month
Toenails grow much more slowly, about 1 mm per month (roughly one third of the fingernail rate)

How to calculate measure the distance in millimetres from the cuticle at the nail base to the middle of the groove, then divide by the growth rate per month.

Distance from nail base to groove	Fingernail (~3 mm/month)	Toenail (~1 mm/month)
1.5 mm	About 2 weeks ago	About 1.5 months ago
3 mm	About 1 month ago	About 3 months ago
6 mm	About 2 months ago	About 6 months ago
9 mm	About 3 months ago	About 9 months ago

A real example You see a horizontal groove across your index fingernail, about 3 mm from the cuticle. Fingernails grow about 3 mm per month, so nail production paused about 1 month ago. If you look back and find that you had a high fever or were in hospital that month, this explains the groove completely without any further tests.

Another example with a toenail A groove is 4 mm from the base of the big toenail. Toenails grow about 1 mm per month, so this takes you back about 4 months, which often matches a time when your child had hand-foot-and-mouth disease or when you were seriously ill.

Cautions when interpreting the result These figures are estimates. Nails grow more slowly in older adults, in people with poor circulation to the fingers and toes, with malnutrition, and in cold weather, so use this as a clue rather than a fixed answer.

What causes wavy toenails? How do they differ from fingernails?

Wavy toenails have a different set of causes from fingernails, because toenails sit in damp shoes, are pressed repeatedly and grow much more slowly. The two most common causes are

Nail fungus (Onychomycosis) — the nail thickens, turns yellow or brown, has a rough, irregularly wavy surface and crumbly debris under the nail, and often starts in one big toenail before spreading. This group is clearly different from age-related vertical ridges, because the waves are uneven and the nail is also abnormally thick.
Repeated pressure from shoes (Repetitive shoe trauma) — common in people who wear narrow-toed shoes, high heels or who run. The big toenail and second toenail become thick, rough and wavy, and sometimes there is bleeding under the nail.

Why it matters to tell these two apart because the treatments are very different. A thick, wavy nail caused by shoes improves when you change your shoes, but if it is fungus and left untreated, it spreads and can infect other nails. On the other hand, taking antifungal medication for a long time when you do not actually have a fungal infection carries side-effect risks for no reason. Dermatologists therefore usually scrape the nail and send it for testing to confirm before starting medication.

Other toenail problems that are often seen together and should be told apart include ingrown toenails and inflammation of the tissue around the nail (paronychia). Both can make the nail grow out misshapen and wavy, but they are treated differently.

Which vitamin deficiency causes wavy nails? A straight answer from a doctor

The short answer: most of the time, you are not deficient in any vitamin. This is the most common misunderstanding about nails, and the reason many people spend money on supplements without benefit.

Common vertical wavy nails are caused by ageing and dryness of the nail plate, not a vitamin deficiency. Taking vitamin supplements when your body is not truly deficient therefore does not make vertical ridges go away.

Facts worth knowing

Iron — iron deficiency makes nails thin and scooped like a spoon (Koilonychia). It does not cause wavy nails or ridges. This is a very common mix-up.
Biotin — the medical evidence is very weak. The available studies are small and were done in people with brittle nails, not in people whose nails are wavy due to age. High-dose biotin can also interfere with thyroid blood tests and cardiac enzyme tests.
Calcium — white spots on the nails (Leukonychia) do not mean calcium deficiency. Most are caused by minor knocks at the nail base and grow out on their own.
Severe nutritional deficiency — can genuinely affect nail formation, but it is seen in clear malnutrition, not in people who eat a normal balanced diet.

Plainly put: if you have mild vertical wavy nails and are otherwise healthy, you do not need to buy supplements. But if your nails change together with tiredness, paleness or hair loss, a blood test for iron deficiency or thyroid problems will be much more to the point.

The same applies to brittle nails and nails that peel in layers, which are a different condition from wavy nails but are often mistaken for the same thing. Wavy nails means the nail surface is uneven, whereas brittle nails means the keratin layers separate. Both respond better to reducing contact with water and chemicals than to taking supplements.

Pitted nails together with waves — when waves are linked to a skin disease

If the nail surface is rough and wavy together with tiny pits (nail pitting) as if pricked by a needle, or the nail is abnormally thick, this group is usually linked to skin diseases that affect the nail base, including

Nail psoriasis — pitting, thickened nails, debris under the nail, oil-drop spots, and the nail may lift from the nail bed.
Patchy hair loss (Alopecia areata) — the nails have tiny pits arranged in a regular, grid-like pattern.
Eczema around the nail — makes the nail surface uneven, with irregular horizontal waves.
Trachyonychia (sandpaper-like rough nails) — the whole nail surface is rough and several fingers may be affected. It occurs in children and often improves gradually on its own.

This group does well when the underlying disease is correctly diagnosed and that disease is treated, not just the nail surface. A dermatologist will also examine the rest of your skin and scalp to confirm.

Nail warning signs that need a doctor soon

Most wavy nails are not dangerous, but some features should be examined by a dermatologist with a dermoscope so that an important disease is not missed, including:

A single brown or black vertical band (Melanonychia), especially when the band widens, has an irregular edge or uneven colour.
Colour spreading onto the skin or the skin around the nail (Hutchinson's sign) — a sign that needs immediate examination to rule out subungual melanoma.
A damaged, crumbling or detaching nail plate together with a lump or bleeding under the nail without any injury.
One nail that is misshapen, wavy or thickening progressively, unlike the other fingers.
Wavy nails together with general symptoms such as tiredness, paleness, joint pain or weight loss.
Beau's lines that keep recurring for no known reason.

Remember subungual melanoma usually starts as a single band of colour on one finger, not as many waves on every finger, so there is no need to worry too much if your ridges look the same on all fingers.

How to care for and treat wavy nails

For ordinary harmless vertical ridges, the goal is to keep the nails strong and make them look smoother.

Moisturise the nails and the skin around them with a cream or moisturiser, especially one containing urea or lactic acid, applied after washing your hands and before bed.
Avoid damaging the nails, for example scrubbing the nail surface hard, pushing back or cutting the cuticle deeply, and frequently using nail polish remover containing acetone.
Wear gloves when doing housework or handling chemicals and cleaning products.
Trim the nails to a suitable length and file gently in one direction, not back and forth, and do not buff the nail surface thinner to remove the ridges, as this will make the nail more brittle.
Choose shoes with a wide enough toe box if your toenails are wavy from pressure.
Treat the underlying disease if the ridges are linked to psoriasis, lichen planus, fungus or iron deficiency.

Changes show up slowly because a fingernail takes about 4-6 months to grow out completely, and a toenail up to 12-18 months, so consistency and patience are needed.

When should you see a dermatologist?

See a dermatologist when your wavy nails come with any of the following: a black or brown vertical band, a change affecting just one nail that keeps getting worse, pitting or abnormally thick nails, thick yellow toenails suspected of fungus, general symptoms, or when you are worried and want a clear answer.

A dermatologist can examine the nail with a dermoscope, scrape the nail to test for fungus, and examine the rest of your skin to tell clearly whether it is just ageing or an underlying disease. Our principle is to get the diagnosis right first, then treat precisely.

Frequently asked questions

What causes vertical ridges in the nails, and are they dangerous?

Vertical ridges running from the nail base to the tip are mostly caused by ageing and dryness of the nail plate. They are not dangerous and do not need treatment if they look the same on every finger and the nails do not change colour or hurt. But if there is a single deep line on one finger, or a thin, fragile nail, nail lichen planus should be ruled out.

What causes horizontal ridges in the nails?

Horizontal ridges are Beau's lines, which form when nail production at the nail base pauses temporarily. Common causes are high fever, severe illness, chemotherapy, hand-foot-and-mouth disease and injury to the nail base. If they appear at the same position on several fingers at once, they usually reflect an event that affected the whole body. If it is one finger, it is usually a local injury.

Which vitamin deficiency causes wavy nails?

Most of the time, you are not deficient in any vitamin. Common vertical ridges are caused by age and dry nails. Iron deficiency makes nails thin and spoon-shaped (Koilonychia), not wavy. The evidence for biotin is very weak and was studied mainly in people with brittle nails, so supplements are not needed unless a deficiency has actually been found.

What causes wavy toenails, and are they different from fingernails?

Yes, they differ. The main causes of wavy toenails are nail fungus (Onychomycosis), which makes the nail thick, yellow and irregularly rough, and repeated pressure from tight or narrow shoes. The two are treated differently, so the nail should be scraped and tested to confirm fungus before starting antifungal medication.

Can you work out when a horizontal groove was caused?

Yes. Fingernails grow about 0.1 mm per day, or roughly 3 mm per month, and toenails about 1 mm per month. Measure from the cuticle to the middle of the groove and divide by the growth rate. For example, a groove 3 mm from the base of a fingernail means the event was about 1 month ago. This is an estimate, because nails grow more slowly in older adults and in people with poor circulation to the fingers and toes.

Can wavy nails go away on their own?

Horizontal ridges from a single event, such as a high fever, usually grow out on their own as the nail lengthens, within a few months. Age-related vertical ridges usually stay but are harmless. Keeping the nails moisturised can make them look smoother. A fingernail takes about 4-6 months to grow out completely, and a toenail up to 12-18 months.

Which wavy nails carry a cancer risk?

What to watch for is not waves but a single brown or black vertical band that widens, has an irregular edge, or has colour spreading onto the skin around the nail (Hutchinson's sign), as well as a destroyed nail plate or a lump under the nail on one finger that keeps getting worse. These should be examined by a dermatologist with a dermoscope to rule out subungual melanoma.

References

DermNet NZ. Beau lines. https://dermnetnz.org/topics/beau-lines
DermNet NZ. Melanonychia. https://dermnetnz.org/topics/melanonychia
DermNet NZ. Fungal nail infections (onychomycosis). https://dermnetnz.org/topics/fungal-nail-infections
Yaemsiri S, Hou N, Slining MM, He K. Growth rate of human fingernails and toenails in healthy American young adults. Journal of the European Academy of Dermatology and Venereology. 2010;24(4):420-423.
Singal A, Arora R. Nail as a window of systemic diseases. Indian Dermatology Online Journal. 2015;6(2):67-74.
Fawcett RS, Linford S, Stulberg DL. Nail abnormalities: clues to systemic disease. American Family Physician. 2004;69(6):1417-1424.
Bolognia JL, Schaffer JV, Cerroni L, editors. Dermatology. 5th ed. Elsevier; 2024. Chapter on nail disorders.
UpToDate. Overview of nail disorders. Wolters Kluwer. (Database for healthcare professionals)

The information in this article is for general understanding only. It is not a diagnosis and does not replace an examination by a doctor. If you have any abnormal symptoms, see a dermatologist for an individual diagnosis.

Written by Dr. Patara Voravutinon, Dermatologist · Last reviewed July 30, 2026