Beau's Lines: What Those Horizontal Grooves in Your Nails Mean

What Are Beau's Lines?

Beau's lines are transverse (side-to-side) grooves or ridges that run horizontally across the nail plate. Named after the French physician Joseph Honoré Simon Beau, who described them in the 19th century, they are not a disease in themselves — they are a physical marker that your nail matrix (the growth center of the nail at its base) was temporarily disrupted at some point in the past.

Think of Beau's lines as a growth ring on a tree trunk: they mark a specific period of stress. Because nails grow at a predictable rate — about 3 mm per month for fingernails, slower for toenails — a dermatologist can actually estimate when the disruption occurred by measuring how far the groove is from the base of the nail.

Beau's lines are very common. Almost any significant physical or emotional stress can trigger them, and they became widely recognized during the COVID-19 pandemic when many people noticed grooves appearing in their nails 1-2 months after recovering from the illness.

What Do Beau's Lines Look Like?

Beau's lines appear as a horizontal depression or groove crossing the nail plate from one side to the other. Key features include:

• Location: they cross the width of the nail, perpendicular to nail growth (as opposed to vertical ridges, which are a normal aging change)
• Depth: they can be subtle (a faint indentation you feel more than see) or deep (a noticeable groove)
• Number: one groove per disruption; multiple grooves indicate multiple episodes of stress or illness over time
• Which nails: if all nails are affected simultaneously, the cause was a body-wide event (systemic illness, major surgery, chemotherapy); if only one nail has a groove, a local cause is more likely (injury to that finger, nail infection)
• Movement: because the nail keeps growing, the groove will gradually move toward the tip of the nail over weeks and months until it grows off

What Causes Beau's Lines?

The nail matrix pauses or slows its activity whenever the body is under significant stress. Common causes include:

Systemic (Whole-Body) Causes

• Serious infections: high fevers from any cause, pneumonia, COVID-19, measles, scarlet fever, hand-foot-mouth disease
• Major surgery: especially procedures requiring general anesthesia
• Heart attack or stroke
• Severe nutritional deficiency: prolonged periods of poor nutrition or malabsorption
• Chemotherapy: cancer drugs often temporarily halt nail growth; multiple cycles may produce multiple grooves
• Severe psychological stress: intense emotional trauma can trigger Beau's lines in some people
• Metabolic disorders: uncontrolled diabetes, thyroid disease, kidney failure

Local (Single Nail) Causes

• Trauma directly to the nail matrix (crushing, slamming in a door)
• Paronychia (skin infection around the nail base) pressing on the matrix
• Ill-fitting acrylic nail systems putting pressure on the nail base

Are Beau's Lines Serious?

Beau's lines themselves are harmless — they are just a groove in the nail that will grow out. What matters is understanding what caused them. In many cases, especially after a well-known illness, major surgery, or chemotherapy, the cause is already clear and no further workup is needed.

However, if you notice Beau's lines on all your nails and cannot identify an obvious cause — or if they keep recurring — that warrants a medical evaluation. Recurrent or unexplained Beau's lines can be an early clue to a systemic condition like poorly controlled diabetes, thyroid disease, or kidney problems that needs attention.

How Long Do Beau's Lines Last?

Beau's lines do not fade — they grow out. At a fingernail growth rate of about 3 mm per month, a groove that forms at the base of the nail takes roughly 6 months to reach the tip and be clipped away. Toenails grow more slowly (about 1-1.5 mm per month) so Beau's lines on toenails may take 12-18 months or longer to fully grow off.

There is no treatment to speed up this process — but the good news is that most nails return to completely normal appearance once the groove grows out, assuming the underlying cause has been resolved.

Treatment: What Can Be Done?

For Beau's lines themselves, treatment focuses on two things:

1. Identifying and treating the underlying cause if it is ongoing (e.g., optimizing blood sugar control, treating a thyroid condition, addressing nutritional deficiencies)
2. Nail care while waiting for growth: keeping nails moisturized and protected, avoiding activities that might crack or break the nail at the groove (the indentation is a weak point), and using a clear nail hardener if the groove is deep and the nail feels fragile

There is no topical or oral treatment that fills in or reverses a Beau's line — it simply needs time to grow out.

Beau's Lines vs. Other Nail Changes

It helps to know what Beau's lines are not:

• Vertical ridges: run lengthwise from base to tip; very common with aging and usually harmless (not Beau's lines)
• Mee's lines: white horizontal bands (not grooves) associated with arsenic poisoning or certain medications
• Muehrcke's lines: paired white bands on the nail associated with low albumin (a blood protein); they do not move as the nail grows
• Habit-tic deformity: a washboard-like series of transverse ridges from repetitive picking at the cuticle of the same nail

When to See a Dermatologist

• You notice Beau's lines on multiple nails with no obvious explanation
• The groove is unusually deep or the nail feels like it might split
• You see Beau's lines recurring on the same nails
• The groove is accompanied by color changes, nail thickening, or other nail abnormalities
• You want to confirm the groove is indeed a Beau's line and rule out other nail conditions

Frequently Asked Questions

I had COVID-19 two months ago and now have grooves in my nails. Is this normal?

Yes — Beau's lines following COVID-19 became one of the most widely reported nail findings of the pandemic. The timing fits perfectly: nails typically take 4-8 weeks after a systemic illness to show the groove at a visible position on the nail plate. These grooves are benign and will grow off completely. No treatment is needed unless you are concerned about an underlying health issue.

I only have a groove on one fingernail. What does that mean?

A single affected nail is usually the result of local trauma or a localized nail problem — for example, slamming that finger in a door, a previous nail infection, or pressure from an ill-fitting acrylic nail. Systemic causes typically affect all nails simultaneously. If you cannot recall any local injury and multiple nails develop grooves, a broader evaluation makes sense.

Can vitamins or supplements get rid of Beau's lines faster?

No supplement can erase a groove that is already in the nail plate. Nails do require adequate nutrition to grow healthily — biotin, zinc, iron, and protein all play roles — and correcting a true deficiency may support better nail growth going forward. But if your nutrition is adequate, additional supplements will not noticeably speed nail growth or eliminate the groove.

I have multiple grooves across all my nails. Should I be worried?

Multiple grooves indicate multiple episodes of stress, illness, or treatment (such as repeated chemotherapy cycles). If you have had several serious illnesses or major surgeries in recent years, this may explain the pattern. If you cannot account for the grooves, see a dermatologist or your primary care physician for evaluation of possible systemic causes.

Trusted Resources

• American Academy of Dermatology — Nail Health
• Mayo Clinic — Nail Ridges

Always consult a board-certified dermatologist for diagnosis and personalized treatment recommendations. This information is for educational purposes only and does not replace professional medical advice.