Beau's Lines on Nails: Causes, Meaning, and When to Worry

What Are Beau’s Lines?

Beau’s lines are transverse depressions, or grooves, that form across the surface of the nail plate. They reflect a temporary interruption in the normal growth of the nail and appear as deep horizontal furrows running from one side of the nail to the other, on the fingernails, the toenails, or both.

The condition is named after the French physician Joseph Honore Simon Beau, who first described these nail grooves in the 19th century after noticing their connection to serious systemic illness in his patients.

Although Beau’s lines are often dismissed as a harmless finding, or attributed simply to a temporary stressful event, they can in fact serve as an important early warning sign of an underlying acute or chronic health condition. Because the nail matrix, the tissue responsible for producing new nail, is highly sensitive to changes in the body’s overall metabolic state, almost any significant physical or emotional stressor has the potential to leave a visible mark on the nails weeks or months later.

Understanding what Beau’s lines look like, what causes them, and when they warrant medical attention can help patients and caregivers recognize a potentially meaningful clue about their overall health.

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What Do Beau’s Lines Look Like?

Beau’s lines can affect all of the nails, or only a few, such as the thumbnails and big toenails, which tend to grow more slowly and are therefore more likely to show visible changes. In some cases, a person may notice just a single horizontal groove, while in others, especially when the underlying cause is cyclical, such as repeated cycles of chemotherapy, multiple evenly spaced lines may appear across the same nail, each one corresponding to a separate cycle of treatment.

As the nail continues to grow, the groove gradually moves away from the nail matrix (cuticle) and toward the free edge (tip) of the nail. This predictable growth pattern is clinically useful, because it allows doctors to work backward and estimate approximately when the triggering event occurred, based on how far the line has traveled from the base of the nail. This is possible because nail growth occurs at fairly consistent, well-documented average rates:

• Fingernails grow at an average rate of about 1 millimeter every 6 to 10 days, which translates to roughly 2 to 3 millimeters per month.

• Toenails grow more slowly, at an average rate of approximately 1 millimeter per month.

By measuring the distance between the cuticle and the visible groove, a clinician can estimate, with reasonable accuracy, how many weeks or months earlier the causative event took place, which can be extremely helpful when trying to correlate the nail finding with a specific illness, medication, or life event in the patient’s recent history.

The specific characteristics of the lines, including their number, depth, width, and position on the nail, can offer important clues about the nature and timing of the underlying cause:

• A single line on just one nail often points toward a localized cause, such as direct trauma to that specific finger or toe.

• Multiple lines affecting most or all of the nails are more suggestive of a systemic problem, meaning a condition affecting the entire body, such as a severe infection, a metabolic disturbance, or a course of chemotherapy.

• The depth of the groove can reflect the severity or duration of the triggering event, deeper lines generally correspond to more severe or prolonged episodes of illness or stress.

• Evenly spaced, repeating lines on the same nail strongly suggest a cyclical process, most classically seen with repeated chemotherapy cycles.

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Causes

Beau’s lines form when there is a temporary interruption in keratin production within the nail matrix, the specialized tissue located under the cuticle from which the nail plate originates. This growth arrest can be triggered by acute systemic events, such as high prolonged fever, severe infections, physical trauma, or chemotherapy, or by chronic diseases that act more subtly and repeatedly over time, gradually wearing down the nail matrix’s ability to function normally.

The underlying causes of Beau’s lines are numerous and can be grouped into several broad categories:

Acute systemic causes

• Severe febrile infections (for example, pneumonia, sepsis, COVID-19)
• Major surgical procedures
• Childhood exanthematous (rash-causing) illnesses
• Acute organ failure (liver, kidney)

Drug-related and iatrogenic causes

• Chemotherapy agents (for example, taxanes, doxorubicin, cisplatin)
• Immunosuppressive therapies
• Radiation therapy

Dermatologic conditions

• Nail psoriasis
• Chronic hand eczema
• Lichen planus

Mechanical trauma

• Repeated microtrauma (for example, contact sports)
• Aggressive or overly invasive manicures

Malnutrition and nutritional deficiencies

• Severe protein deficiency
• Severe hypocalcemia (low blood calcium)
• Zinc or iron deficiency (though the supporting evidence here is less robust)

Chronic systemic diseases

• Poorly controlled diabetes mellitus
• Peripheral vascular disease
• Systemic lupus erythematosus

Each of these categories is explored in more detail in the sections below, since understanding the specific trigger can help guide any further evaluation that may be needed.

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Infections

Illness, or really any significant stress placed on the body, can interrupt normal nail growth, because when the body is actively fighting an infection, it temporarily redirects energy and resources away from processes considered non-essential for immediate survival, including hair and nail growth.

A wide range of infections has been associated with the appearance of Beau’s lines. This includes essentially any illness capable of producing high fever (discussed in more detail below), such as scarlet fever, measles, mumps, and pneumonia.

More recently, COVID-19 infection has also been linked to the development of these nail changes, an observation that gained significant attention during the pandemic as clinicians noticed patients developing Beau’s lines weeks after recovering from acute infection. Other viral illnesses, such as hand, foot, and mouth disease, and more severe infections such as syphilis, have also been documented as potential triggers.

In other words, it appears that any infection severe enough to provoke a significant systemic response has the potential to disrupt the delicate process of cell division taking place within the nail matrix, regardless of the specific pathogen responsible.

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Fever

Virtually any illness that causes high fever has the potential to cause Beau’s lines to form.

During an episode of high fever, the body concentrates its available resources on fighting off the underlying infection or inflammatory process, which temporarily compromises the normal, steady growth of the nails. This happens because the cells of the nail matrix, like many rapidly dividing cells in the body, are particularly sensitive to shifts in the body’s metabolic priorities during acute illness.

Because high fever is a common physiological response shared across many different infections and inflammatory conditions, it functions as a general, nonspecific stress factor capable of temporarily diverting resources away from nail production. Importantly, it appears to be the body’s overall response to elevated temperature, rather than the identity of the specific pathogen causing the fever, that most directly affects cellular metabolism and division within the nail matrix. This helps explain why Beau’s lines can appear after such a wide variety of seemingly unrelated febrile illnesses.

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Surgery and Physical Trauma

Beyond infection, intense physical stress, such as that experienced during major surgery or significant physical trauma, can also trigger the formation of Beau’s lines.

Common examples include:

• Blunt trauma, such as accidentally dropping something heavy on a finger or toe
• Exposure to extreme cold, which can temporarily impair blood flow and cellular activity in the extremities
• Crush injuries, such as slamming a finger in a door

In addition to direct physical injury, major medical events such as a heart attack (myocardial infarction, caused by a blockage in the coronary arteries) have also been associated with the subsequent appearance of these nail lines.

It is worth distinguishing between two different mechanisms at play here. Direct physical trauma to a finger or toe can damage the nail matrix itself, directly disrupting local nail cell production. On the other hand, major systemic stress events, such as undergoing a significant surgical procedure or surviving a heart attack, tend to work indirectly, triggering a body-wide stress response that temporarily affects nail growth even in fingers and toes that were never physically injured.

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Emotional Stress

Perhaps surprisingly to some, significant emotional stress, such as going through a divorce, experiencing the death of a family member, losing a job, or living with an anxiety disorder, has also been documented as a potential cause of Beau’s lines.

This connection highlights an important and often underappreciated point: stress, whether mental, emotional, or physical in origin, can genuinely and measurably influence nail health and growth. This phenomenon underscores the deep, well-documented connection between psychological well-being and physical health, demonstrating that even purely emotional distress, without any accompanying physical illness, can manifest through visible, concrete changes in the body, including the nails.

While the exact biological mechanism linking severe emotional stress to nail matrix dysfunction is not yet fully understood, it is thought to involve stress hormones such as cortisol, which can influence cellular metabolism and immune function throughout the body, potentially including the specialized cells responsible for producing the nail plate.

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Chemotherapy

Chemotherapy used in the treatment of cancer is one of the most frequently and consistently documented causes of Beau’s lines in clinical practice.

Chemotherapy agents work by selectively targeting rapidly dividing cells, since cancer cells characteristically divide much faster than most normal cells in the body. Unfortunately, this mechanism does not distinguish perfectly between cancerous cells and other naturally fast-dividing healthy cells in the body, including those found in the nail matrix, hair follicles, and lining of the digestive tract.

The result is a temporary but often pronounced interruption of active cell replication within the nail matrix, which manifests clinically as the formation of these characteristic transverse depressions across the nail plate. Because chemotherapy is typically administered in distinct cycles, with treatment periods followed by recovery periods, patients undergoing multiple rounds of chemotherapy often develop several evenly spaced Beau’s lines on the same nail, each one marking a separate treatment cycle, a pattern that can be a useful visual timeline of a patient’s treatment history.

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Non-Chemotherapy Medications

While chemotherapy is one of the best-documented pharmacological causes, a variety of other systemic medications can also induce the formation of Beau’s lines, even in patients who have never received cancer treatment.

Some medications appear to interfere directly with the proliferation of cells within the nail matrix, in a manner somewhat similar to chemotherapy, though generally to a lesser degree. Others act more indirectly, for example by altering the absorption of key nutrients from the digestive tract, disrupting hormonal balance, or affecting other essential physiological processes that the nail matrix depends on for normal function.

Medications and drug classes that have been associated with Beau’s lines in medical literature include certain retinoids, some antifungal medications used for prolonged periods, certain anticonvulsants, and select antibiotics, though the overall risk with any single non-chemotherapy medication remains considerably lower than with cancer chemotherapy regimens. Patients who notice new Beau’s lines shortly after starting a new medication should mention this to their prescribing physician, since it may be relevant, though it rarely requires stopping an otherwise beneficial treatment.

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Malnutrition and Nutrient Deficiencies

Zinc is an essential trace mineral involved in numerous biological processes throughout the body, including protein synthesis and cell division, both of which are critical for healthy nail formation. Even a moderate zinc deficiency can impair the normal activity of the nail matrix, potentially contributing to the formation of Beau’s lines, although it is worth noting that the scientific evidence specifically linking zinc deficiency to Beau’s lines is somewhat less robust and consistent compared to other well-established causes such as fever or chemotherapy.

Malnutrition more broadly, and particularly severe protein deficiency, has also been associated with the development of Beau’s lines. This connection makes sense from a biological standpoint, since nails are composed primarily of keratin, a fibrous structural protein. When dietary protein intake is insufficient to meet the body’s needs, the synthesis of new nail plate material can become compromised, leading to a temporary slowing or complete, if brief, arrest of nail growth.

Other nutritional factors that have occasionally been linked to nail growth disturbances, though generally with weaker evidence, include severe iron deficiency and significant deficiencies in certain B vitamins. Patients with eating disorders, malabsorption conditions such as celiac disease or inflammatory bowel disease, or those recovering from prolonged illness with reduced food intake may be at particular risk for nutrition-related Beau’s lines.

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Systemic Diseases

A number of chronic and acute diseases affecting major organ systems have been linked to the development of Beau’s lines, often reflecting the significant physiological stress these conditions place on the entire body.

Cardiovascular Disease

Major cardiovascular events, such as an acute myocardial infarction or an episode of congestive heart failure, have been associated with the subsequent appearance of Beau’s lines. These conditions generate substantial systemic stress on the body, which can interfere with the normal proliferation of cells within the nail matrix, potentially through ischemic mechanisms (reduced blood flow and oxygen delivery to tissues) or through generalized inflammatory processes that accompany serious cardiac events.

Kidney Disease

Acute kidney failure is another systemic condition capable of triggering Beau’s lines. When the kidneys are damaged, their ability to maintain the body’s normal metabolic balance, known as homeostasis, becomes compromised. This can lead to the accumulation of waste products and toxins in the bloodstream that would normally be filtered out, disrupting numerous cellular mechanisms throughout the body, including those responsible for the normal growth of nail tissue.

Liver Disease

Liver diseases, particularly in their more advanced stages, can similarly interfere with normal nail growth patterns. The liver plays a central role in protein synthesis and the metabolism of essential nutrients throughout the body. When liver function becomes significantly impaired, whether due to conditions such as cirrhosis, hepatitis, or liver failure, this disruption can lead to secondary changes in the nail matrix, manifesting visibly as Beau’s lines.

Other Associated Systemic Conditions

A wide variety of additional chronic and acute conditions have been documented in association with the development of Beau’s lines, including:

• Uncontrolled diabetes mellitus, particularly during periods of poor glycemic control or acute metabolic crisis
• Hypothyroidism, an underactive thyroid gland, which can slow numerous metabolic processes throughout the body
• Peripheral artery disease (PAD), which reduces blood flow to the extremities, including the fingers and toes
• Raynaud’s phenomenon, a condition causing episodic reduced blood flow to the fingers and toes, often triggered by cold or stress
• Kawasaki disease, a rare but serious inflammatory condition affecting children, which can cause significant systemic inflammation
• Hypoparathyroidism, a condition involving insufficient parathyroid hormone, which can lead to low blood calcium levels affecting numerous body tissues, including nails

Given this extensive list, it becomes clear why Beau’s lines are sometimes described by dermatologists as a nonspecific but clinically meaningful sign, one that should prompt a thoughtful review of a patient’s recent medical history rather than being dismissed outright.

Differential Diagnosis

Beau’s lines must be carefully distinguished from other nail changes that can appear visually similar but arise from entirely different underlying processes. Correctly identifying the specific type of nail change is important, since each has different causes, implications, and, in some cases, different levels of clinical concern:

• Mees’ lines: These appear as transverse white bands across the nail plate, but unlike Beau’s lines, they are not depressed or grooved, they lie flat within the nail plate itself. Mees’ lines are classically associated with arsenic poisoning, though they have also been reported following certain chemotherapy treatments and other forms of severe systemic illness.

• Transverse leukonychia: This condition presents as white, opaque discoloration of the nail plate, often appearing in bands or patches. It is frequently linked to previous physical trauma to the nail or, in many cases, has no identifiable cause at all (idiopathic).

• Transverse onychoschizia: This refers to horizontal splitting or lamellar peeling of the nail plate, most commonly seen in the context of chronic dryness, frequent hand washing, or repeated exposure to harsh chemicals or detergents.

A dermatologist can typically distinguish between these conditions through careful visual examination, sometimes supplemented by dermoscopy (magnified examination of the nail), and by taking a detailed patient history regarding recent illnesses, medications, and exposures.

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When to Worry

In the absence of any serious underlying medical condition, Beau’s lines are generally considered a self-limiting finding, meaning they will resolve on their own as the nail continues to grow outward, without leaving any permanent damage to the nail itself.

However, there are certain situations where the appearance of Beau’s lines should prompt a visit to a healthcare provider for further evaluation:

• Multiple nails affected simultaneously, particularly if most or all fingernails and toenails show similar grooves, since this pattern suggests a systemic cause rather than simple localized trauma.

• No clear history of recent trauma, illness, fever, or significant stress that would otherwise explain the finding, especially when the lines are deep or affect several nails.

• Recurrent or repeated episodes of Beau’s lines over time, which may indicate an ongoing or poorly controlled chronic condition, such as unrecognized diabetes, thyroid disease, or peripheral vascular disease.

• Accompanying symptoms, such as unexplained fatigue, unintentional weight loss, persistent fever, swelling, changes in skin color, or other signs of systemic illness occurring alongside the nail changes.

• Very deep or unusually wide grooves, which may suggest a more prolonged or severe underlying insult to the nail matrix compared to typical, milder cases.

If any of these red flags are present, it is advisable to consult a doctor, who can take a thorough medical history, perform a physical examination, and, if warranted, order basic laboratory tests (such as blood counts, thyroid function tests, kidney and liver function panels, or blood glucose levels) to investigate for an underlying systemic cause.

It is also worth noting that in children, the appearance of Beau’s lines following a febrile illness or a common childhood infection is generally not a cause for alarm and is a well-recognized, benign phenomenon, provided the child has otherwise recovered well from the illness.

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How Are Beau’s Lines Treated?

There is currently no specific treatment that directly targets the nail groove itself. Because Beau’s lines represent a mark left behind by a growth interruption that has, in most cases, already resolved by the time the line becomes visible, the affected portion of the nail simply needs time to grow out naturally and be trimmed away, following the nail growth rates discussed earlier in this article.

However, this does not mean that no action should be taken. Identifying and appropriately treating the underlying cause is essential, both to support overall health and to help prevent the recurrence of Beau’s lines in the future. Depending on what is ultimately found to be responsible, management may include:

• Treating an active infection with appropriate antimicrobial therapy
• Adjusting or discontinuing a medication suspected of contributing to the nail changes, always in consultation with the prescribing physician
• Correcting an identified nutritional deficiency, such as through dietary changes or targeted supplementation under medical supervision
• Optimizing management of a chronic condition, such as improving blood sugar control in diabetes, or adjusting thyroid hormone replacement in hypothyroidism
• Addressing significant psychological stress through appropriate support, counseling, or stress management techniques, when emotional stress is identified as the likely trigger

In general, once the underlying cause has been identified and appropriately managed, or has simply resolved on its own, no further intervention is needed for the nail itself. Practicing good general nail care, such as keeping nails trimmed, avoiding excessive trauma or aggressive manicures, and maintaining a balanced, nutritious diet, can support healthy nail regrowth during the recovery period.

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Frequently Asked Questions

Are Beau’s lines painful?

No, Beau’s lines themselves are not painful and do not cause any discomfort. Any pain experienced around the time the lines form is typically related to the underlying cause, such as a traumatic injury, rather than to the nail groove itself.

How long does it take for Beau’s lines to grow out completely?

This depends on which nail is affected and how close to the cuticle the line originally formed. Since fingernails grow at roughly 2 to 3 millimeters per month, a line near the base of the nail may take several months to reach the tip and be trimmed away. Toenails, which grow more slowly, can take considerably longer, sometimes up to a year or more, to fully grow out.

Can Beau’s lines appear on just one nail?

Yes. A single Beau’s line on one nail, without any similar changes on other nails, most often points to a localized cause, such as direct trauma to that specific finger or toe, rather than a systemic illness affecting the entire body.

Should I see a dermatologist for Beau’s lines?

If the cause is clear, for example, a recent high fever, a known surgery, or an obvious injury, and only one or a few nails are affected, seeing a doctor is generally not urgent. However, if multiple nails are affected without an obvious explanation, or if the lines recur repeatedly, a consultation with a dermatologist or primary care physician is a reasonable and recommended step.

Can Beau’s lines be a sign of nail fungus?

Beau’s lines themselves are not caused by fungal infection and should not be confused with nail changes caused by onychomycosis (nail fungus), which typically causes thickening, discoloration, and crumbling of the nail rather than a transverse groove. However, a person can have both conditions at the same time for entirely unrelated reasons.

Do Beau’s lines mean I have cancer?

Not necessarily. While chemotherapy is a well-documented cause of Beau’s lines, the vast majority of people who develop these nail grooves do so because of far more common and far less serious triggers, such as a recent fever, infection, minor trauma, or significant stress. Beau’s lines alone are not considered a diagnostic sign of cancer, though in the context of other concerning symptoms, they may prompt a doctor to investigate further.

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Sources and Bibliography

• American Academy of Dermatology Association (AAD), Nail Changes That May Indicate a Health Problem
• National Center for Biotechnology Information (NCBI) / StatPearls, Nail Beau’s Lines Overview
• Mayo Clinic, Nail Abnormalities: Symptoms and Causes
• Cleveland Clinic, Nail Health and Disorders
• MedlinePlus, Nail Abnormalities Information
• British Association of Dermatologists, Patient Information Leaflets on Nail Disorders
• Journal of the American Academy of Dermatology, various clinical studies on nail changes following systemic illness and chemotherapy