Mees’ lines are horizontal white bands that stretch across fingernails or toenails, signaling that something went wrong inside the body weeks or months before the lines became visible. They are a form of true leukonychia, meaning the whiteness is baked into the nail plate itself and cannot be pressed away. The list of conditions that produce them is surprisingly long, ranging from arsenic poisoning to chemotherapy to severe infections, and the lines essentially function as a slow-motion diary of physiological stress recorded in keratin.
What Mees’ Lines Look Like
Mees’ lines appear as one or more white, opaque bands running parallel to the lunula (the pale crescent at the base of the nail) across the full width of the nail. They typically show up on multiple nails at the same level, which makes sense given that whatever triggered them was a systemic event affecting all nail matrices at roughly the same time. The bands are flat and smooth, with no palpable ridge or groove when you run a finger across the nail surface. They do not fade or vanish when you press down on the nail, which is a key clinical detail for distinguishing them from lookalike conditions.
Because the white color is embedded within the nail plate, the lines migrate outward as the nail grows. Over weeks and months, you can watch them travel from the base of the nail toward the free edge, eventually growing out and disappearing when you trim your nails. This is in contrast to changes that originate in the nail bed underneath, which stay in place regardless of nail growth.
How They Form
The whiteness of Mees’ lines comes from disrupted keratinization in the distal nail matrix. When a systemic insult hits the body, the cells responsible for building the nail plate temporarily malfunction. Instead of producing normal, transparent keratin, they retain their nuclei in a process called parakeratosis. Those retained nuclei scatter light rather than letting it pass through, which makes that segment of nail look white and opaque rather than its usual translucent pink.1PubMed Central. Narrative Review of Drug-Associated Nail Toxicities in Oncologic Patients The effect is essentially a brief manufacturing defect: the nail factory hiccupped, and the faulty batch keeps moving down the conveyor belt.
This mechanism also explains why the lines are non-blanching. Because the abnormality is structural, within the nail plate itself, pressing down on the nail does not push blood away and change the appearance the way it would with a vascular or nail-bed phenomenon.2Actas Dermo-Sifiliográficas. Challenging Case White Bands on the Nails: A Diagnostical Clue
What Causes Them
Mees’ lines were first described in the context of arsenic poisoning, and that association remains one of the best known. Arsenic has a particular affinity for keratin-rich tissues like nails and hair, which is why chronic or acute exposure tends to leave visible traces there.3PubMed Central. Nail Manifestations in COVID-19: Insight into a Systemic Viral Disease But the classic arsenic story is only the beginning. The lines appear after a wide range of systemic stressors, and the common thread is that any severe enough illness or toxin can temporarily derail nail matrix function.
Documented triggers include:
- Heavy metal poisoning: arsenic (the classic cause) and thallium toxicity.
- Chemotherapy: drugs like docetaxel, cytarabine with daunorubicin, and cyclophosphamide-based regimens have all been associated with Mees’ lines.4PubMed Central. Nail Changes Induced by Chemotherapeutic Agents
- Organ failure: acute renal failure, congestive heart failure, and myocardial infarction.
- Infections: severe pneumonia, malaria, and even parasitic infections like helminthic and amebic disease.5PubMed. Mees’ lines in a patient with multiple parasitic infections
- Inflammatory and autoimmune conditions: systemic lupus erythematosus, ulcerative colitis, and psoriasis.
- Other severe illnesses: Hodgkin’s disease, sickle cell anemia, pellagra, and high fevers from infectious diseases.6Archives of Internal Medicine. Transverse White Lines in the Fingernails After Acute and Chronic Renal Failure
More recently, Mees’ lines were documented in a previously healthy 57-year-old man following bilateral COVID-19 pneumonia, with the white bands appearing on all ten fingernails.7PubMed Central. Nail Manifestations in COVID-19: Insight into a Systemic Viral Disease That case reinforced the idea that the lines are not specific to any one disease. The severity of the underlying illness matters more than its identity. As researchers noted decades ago, it is probably the acute and serious nature of the underlying condition that provokes the lines, through a nonspecific effect on nail growth.8Archives of Internal Medicine. Transverse White Lines in the Fingernails After Acute and Chronic Renal Failure
Using Nail Growth to Estimate Timing
One of the more useful aspects of Mees’ lines is that they serve as a rough timeline. Because fingernails grow at a fairly predictable rate, about 1 mm every six to ten days, you can measure how far a white band has traveled from the base of the nail and work backward to estimate when the triggering event occurred.9TheScientificWorldJournal. Mees’ lines
This is particularly helpful in two scenarios. In suspected poisoning cases, the position of the lines can help narrow down when exposure happened. In cancer patients receiving cyclical chemotherapy, the spacing between multiple Mees’ lines on the same nail can correspond to the intervals between treatment cycles. If someone had chemo every three weeks, you might see white bands roughly 3 mm apart, each one marking a round of treatment. The nail essentially keeps a receipt.
The limitation is that nail growth varies between individuals and even between fingers on the same hand. Thumbnails grow more slowly than index fingernails, for instance, and toenails grow roughly half as fast as fingernails. Age, nutrition, and circulation all affect the rate. So the timeline estimate is approximate, not forensic-grade precise, but it can be clinically valuable when combined with a patient’s history.
Telling Mees’ Lines Apart from Lookalikes
Several other nail conditions produce white horizontal markings, and they are easy to confuse if you do not know what to look for. The two most commonly mixed up with Mees’ lines are Muehrcke’s lines and Beau’s lines.
Muehrcke’s Lines
Muehrcke’s lines also appear as white transverse bands, but they originate in the nail bed rather than the nail plate. The practical test is simple: press down on the nail. Muehrcke’s lines disappear under pressure because compressing the nail bed pushes away the underlying vascular pattern that creates the white appearance. Mees’ lines, by contrast, stay put because the whiteness is embedded in the nail plate itself.10Actas Dermo-Sifiliográficas. Challenging Case White Bands on the Nails: A Diagnostical Clue Another telltale difference: Muehrcke’s lines do not migrate outward as the nail grows, because the nail bed is stationary. Mees’ lines move toward the free edge over time.
Muehrcke’s lines are classically associated with low albumin levels (hypoalbuminemia), such as in nephrotic syndrome or liver disease, whereas Mees’ lines reflect a broader category of systemic insult. The distinction matters because the treatment implications differ. Correcting the albumin level can resolve Muehrcke’s lines relatively quickly, while Mees’ lines simply have to grow out.
Beau’s Lines
Beau’s lines are transverse depressions or grooves that you can feel when you run a finger across the nail. They result from a temporary complete arrest of nail plate production, which is a step beyond the partial dysfunction that produces Mees’ lines. Where Mees’ lines represent the nail matrix making defective keratin, Beau’s lines represent the matrix stopping production altogether for a brief period.11Annals of Dermatology. Nail Change after Chemotherapy: Simultaneous Development of Beau’s Lines and Mees’ Lines Both conditions can actually appear on the same nail simultaneously, which has been documented in chemotherapy patients. In those cases, the Beau’s line groove and the Mees’ line white band appear at the same horizontal level, reflecting two different manifestations of the same toxic insult to the matrix.
The triggers overlap heavily. Many of the same illnesses and drugs that cause Mees’ lines also cause Beau’s lines. The specific pattern a person develops seems to depend on how severely and for how long the nail matrix was disrupted rather than on which particular illness was responsible.
Mees’ Lines in Chemotherapy Patients
Nail changes are common during cancer treatment, and Mees’ lines are among the most recognizable. In one study of 125 patients receiving various chemotherapy regimens, about 12% developed Mees’ lines. The drugs involved included docetaxel and combinations of cytarabine with daunorubicin, as well as cyclophosphamide, doxorubicin, vincristine, and prednisolone.12PubMed Central. Nail Changes Induced by Chemotherapeutic Agents Other nail effects like acute paronychia (painful inflammation around the nail fold) were also common, but Mees’ lines were the most frequent purely cosmetic change.
The lines tend to appear with a delay. Because the insult happens at the nail matrix and the affected keratin has to grow out far enough to be visible, you usually do not see the white band until several weeks after the chemotherapy cycle that caused it. This lag can make it tricky to connect a specific nail change to a specific treatment round without thinking about the growth rate math described earlier.
One reassuring point: these nail changes from chemotherapy are generally self-limited. Once treatment ends, the nail matrix resumes normal function, and the white bands eventually grow out entirely. The delay going in also applies going out, so patients sometimes see lines still appearing or still present on their nails for months after finishing treatment.13JEADV Clinical Practice. Nail Toxicities Associated With Anticancer Therapies in Children Fingernails typically take about six months to fully regrow from base to tip, and toenails take considerably longer.
What About Children?
Nail toxicity from chemotherapy also affects children, though the literature is thinner. In one pediatric study, ten children developed nail changes during chemotherapy. The breakdown was five with Muehrcke’s lines, three with Beau’s lines, and one with Mees’ lines.14PubMed. Nail changes associated with chemotherapy in children There was no clear pattern linking a specific cancer type or chemo regimen to a specific nail change, suggesting that in kids as in adults, the lines reflect a general stress response in the nail matrix rather than a drug-specific toxicity.
A broader review of anticancer-associated nail changes in children noted that conventional chemotherapy commonly induces leukonychia (the umbrella term that includes Mees’ lines), Beau’s lines, and other nail abnormalities because the rapidly dividing matrix cells are collateral damage from drugs designed to target cell division.15JEADV Clinical Practice. Nail Toxicities Associated With Anticancer Therapies in Children These changes generally resolve on their own but can take months because of how slowly nails grow. For children and parents, the delayed onset and slow resolution can be confusing and distressing, since the visible damage seems to worsen even after the causative treatment has stopped.
Arsenic and the Forensic Angle
The arsenic connection gives Mees’ lines a forensic dimension that most nail findings lack. In historical poisoning cases, before modern toxicology could detect trace metals in blood, the presence of white transverse bands on the nails was considered a major clinical clue. Arsenic deposits preferentially in keratin-rich structures, so nails and hair become repositories of exposure evidence long after the metal has cleared from the bloodstream.16PubMed Central. Nail Manifestations in COVID-19: Insight into a Systemic Viral Disease
Modern analytical techniques have made it possible to go well beyond just spotting the white lines. Synchrotron X-ray fluorescence microscopy can map the spatial distribution of trace elements within a nail sample, and X-ray absorption spectroscopy can identify the specific chemical form of arsenic present, both with minimal sample preparation.17PubMed Central. Trace Element Distribution and Arsenic Speciation in Toenails as Affected by External Contamination and Evaluation of a Cleaning Protocol These techniques can distinguish between arsenic that was deposited internally through systemic exposure and arsenic that may have contaminated the nail surface externally, from soil or water, which matters enormously for both forensic and epidemiological purposes.
In environmental health research, toenail clippings have become a practical biomarker for chronic low-level arsenic exposure. Toenails are preferred over fingernails partly because they are less prone to external contamination from hand washing and contact with surfaces, and partly because their slower growth rate means each clipping captures a longer window of exposure history.
When Mees’ Lines Appear Without an Obvious Cause
Most of the time, Mees’ lines show up in someone who already knows they are seriously ill. A chemotherapy patient notices them mid-treatment. A person recovering from kidney failure spots them weeks after discharge. The lines confirm what was already known, and their main clinical value is in the timing information they encode.
Occasionally, though, the lines appear in someone who did not realize they had a significant systemic problem, and that is when they become a more powerful diagnostic clue. A case report documented Mees’ lines in a patient with parasitic infections (helminthic and amebic) and no history of arsenic exposure, demonstrating that even non-life-threatening but chronic systemic illness can produce the finding.18PubMed. Mees’ lines in a patient with multiple parasitic infections For clinicians, the takeaway is that Mees’ lines always warrant investigation into what systemic event preceded them. The lines themselves are harmless and do not require treatment, but they serve as a physical record that something disrupted normal physiology several weeks earlier.
Mees’ lines have also been reported after high-altitude mountaineering, reinforcing that the physiological stress does not have to come from disease or toxins. Extreme environmental stress can trigger the same temporary disruption in nail matrix keratinization. The lines in those cases grow out just as they would from any other cause.
Why They Affect All Nails at the Same Level
One of the features that makes Mees’ lines recognizable at a glance is that when they appear, they tend to show up at the same horizontal level across multiple nails. This makes intuitive sense: if a systemic event caused the disruption, all ten nail matrices experienced it simultaneously. The white band then grows outward at whatever rate that particular nail grows. Since different fingers grow their nails at slightly different speeds, the lines may not stay perfectly aligned over time, but at the point of formation they are synchronized.
This multi-nail, same-level pattern is also what separates true Mees’ lines from traumatic leukonychia, the white spots and streaks you get from banging your nail on a countertop. Trauma-related white marks tend to be random in shape, size, and location. They appear on one or two nails, not all of them, and they are not aligned across fingers. If a patient has white transverse bands on all nails at the same level, that alone points toward a systemic cause rather than a local injury.
The multiplicity is also what makes Mees’ lines potentially helpful in detecting intermittent exposure. In arsenic poisoning cases where someone was exposed repeatedly, each exposure event can leave its own white band, producing a series of parallel lines on the same nail. The spacing between the lines reflects the time between exposures, which in retrospect can help reconstruct a pattern of dosing in forensic investigations. Similarly, cyclical chemotherapy leaves its own signature of evenly spaced bands that correspond to treatment intervals.19TheScientificWorldJournal. Mees’ lines
Cosmetic Concerns and Prognosis
For people who develop Mees’ lines, especially those going through chemotherapy, the visual change can be unexpectedly upsetting. Nail changes are often not discussed ahead of treatment because hair loss gets most of the conversation around visible side effects. When the white lines show up, patients sometimes worry they indicate worsening disease or a new problem, when in reality they are delayed evidence of a past insult that has already happened.
There is no treatment for Mees’ lines themselves. No topical product, supplement, or nail treatment will speed their removal. The only resolution is time: the affected section of nail has to grow to the free edge and be trimmed off. For fingernails, this process takes roughly four to six months from formation to elimination. For toenails, it can take a year or longer. The underlying condition is what matters; once it is treated or resolved, the nail matrix resumes normal keratin production, and all new nail growth behind the white band will look normal.
Nail cosmetics like polish or nail wraps can cover the lines if their appearance is bothersome. There is no medical reason to avoid these, and for patients who feel self-conscious, camouflaging the lines during the grow-out period is entirely reasonable. The lines carry no risk of structural weakness to the nail, unlike Beau’s lines, where the groove can make the nail more prone to catching or breaking at that point.