Why Do My Toenails Have White Lines?

White lines on your toenails are almost always a form of leukonychia, a broad term for white discoloration of the nail. The most common explanation is minor, repeated trauma to the nail, which disrupts the way nail cells form and traps tiny air pockets that look white. But the pattern, shape, and behavior of those white marks matter, because some types point to fungal infections, nutritional problems, or underlying health conditions worth investigating. Understanding what your toenails are actually showing you starts with learning to read a few visual clues.

How White Marks Form in the Nail

Your nail grows from a structure called the matrix, tucked under the cuticle at the base. As new cells are produced and pushed forward, they harden into the translucent plate you see. When something disrupts that process, the affected cells may not harden properly, and microscopic irregularities scatter light instead of letting it pass through. The result is a patch or line that looks white even though nothing white has been deposited there. Depending on where the disruption happens and what caused it, the white marks take different shapes and behave differently over time.

Clinicians sort white nail changes into three broad buckets. True leukonychia originates in the nail matrix itself and is baked into the nail plate, so the white area grows out with the nail. Apparent leukonychia comes from changes in the nail bed underneath, so the white area stays put while the nail slides over it. And pseudoleukonychia sits on the surface of the nail plate, typically caused by a fungal invasion from the outside.

The Most Common Culprit Is Everyday Trauma

If you see scattered white dots or short, irregular white lines on one or two toenails, the likeliest explanation is mechanical injury. Stubbing a toe, wearing tight shoes, running, or even a particularly aggressive pedicure can damage the matrix just enough to produce a small cluster of poorly formed cells. These marks are known as punctate leukonychia when they appear as dots and striate leukonychia when they form thin lines. They are harmless, require no treatment, and grow out on their own as the nail advances.

Toenails grow slowly, roughly a millimeter and a half per month for most adults, so a white spot caused by a bump today might not become visible for weeks and can take six months or longer to reach the tip of the nail and disappear. This delay is why people rarely connect the mark to whatever caused it. Children and newborns are especially prone to these marks because their soft, thin nails pick up microtrauma easily; the spots are transient and resolve on their own without any intervention.¹

Fungal Infections That Sit on the Surface

When a fungus invades the top layer of the nail plate rather than burrowing underneath it, the condition is called superficial white onychomycosis.² Instead of the neat dots or thin lines you see with trauma, superficial white onychomycosis tends to produce chalky, irregular white patches on the nail surface. The affected area may feel rough or powdery if you scrape it gently, which is a useful way to distinguish it from true leukonychia caused by matrix disruption.

Toenails are affected far more often than fingernails because feet spend hours in warm, damp shoes. The fungus responsible varies; several species of dermatophytes and molds can cause the same clinical picture. Because the infection is superficial, topical antifungal treatments applied directly to the nail often work well, especially when it is caught early. Left untreated, the white patches can spread and the nail may become thickened, brittle, and harder to manage.

Clinicians can sometimes distinguish pseudoleukonychia from true leukonychia using a dermatoscope. In fungal cases, the surface shows whitish-yellow opaque patches with visible flaking of the nail plate, whereas true leukonychia from matrix disruption shows smooth white bands or dots deeper in the plate without surface irregularity.

Transverse White Bands That Cross the Entire Nail

When white lines run straight across the nail from side to side and appear at roughly the same level on multiple nails, the picture changes considerably. These are not random bumps. Two well-known patterns deserve attention.

Mees’ lines are true leukonychia: bright white, horizontal bands embedded in the nail plate that move forward as the nail grows. They appear when something temporarily poisons or disrupts the distal nail matrix, causing a stripe of abnormally keratinized cells. Classic triggers include heavy-metal poisoning (arsenic and thallium are the textbook examples), severe systemic illness, and cytotoxic chemotherapy drugs. Chemotherapy can arrest the nail matrix’s growth just enough to produce one or more parallel white bands across every nail at the same level.³ Because toenails and fingernails grow at different rates, lines on the toenails may lag behind those on the fingers, but the pattern of simultaneous appearance on all nails at the same level is the hallmark.

Muehrcke lines look similar at first glance but behave differently. They appear as paired white bands separated by strips of normal pink nail. The critical distinction is that Muehrcke lines do not move forward with nail growth, and they temporarily vanish when you press down on the nail. That tells you the whiteness is not embedded in the nail plate itself; it comes from changes in the nail bed underneath, making it an apparent leukonychia. Muehrcke lines are classically tied to low albumin levels in the blood, and they resolve when albumin returns to normal.⁴ The proposed mechanism involves swelling in the nail bed that compresses tiny blood vessels, creating pallor. Conditions that drive albumin low enough to produce these lines include kidney disease with heavy protein loss, liver failure, and severe malnutrition.

When the Whole Nail Turns White

Some conditions produce whitening that covers most or all of the nail rather than discrete lines. Two patterns doctors look for in this category are Terry’s nails and Lindsay’s nails.

Terry’s nails show a ground-glass whiteness over nearly the entire nail plate, with the half-moon at the base hidden and only a narrow band of normal pink remaining at the tip. While they can show up with normal aging, they are also associated with cirrhosis, chronic kidney failure, and congestive heart failure.⁵

Lindsay’s nails, sometimes called half-and-half nails, present with the proximal half white and the distal half reddish-brown, divided by a sharp boundary. The color does not fade with pressure and does not change as the nail grows. This pattern has been linked to chronic kidney disease.⁶

Both Terry’s and Lindsay’s nails are forms of apparent leukonychia. If you notice whitening that covers a large portion of multiple toenails or fingernails, especially combined with fatigue, swelling, or changes in urination, it is worth mentioning to a doctor. On their own, these nail changes are painless and easy to dismiss, but they can be an early visual clue that something systemic deserves investigation.

Psoriasis and Other Skin Conditions

Psoriasis does not only affect the skin. When it involves the nail matrix, it can produce pitting, crumbling, and white spots or bands in the nail plate. The white areas in nail psoriasis are a form of true leukonychia caused by deeper pits forming as the matrix produces irregular cells.⁷ Other matrix-related signs of nail psoriasis include small surface dents, red spots in the lunula, and Beau’s lines, which are horizontal grooves rather than white bands.⁸

Nail psoriasis can be tricky to tell apart from fungal nail infections because both can cause white discoloration, thickening, and crumbling. A dermatologist may need to take a nail clipping or scraping to settle the question, because treatment is entirely different: antifungals for one, immunomodulatory therapy for the other. If you already have psoriasis on your skin or scalp and your toenails develop white patches or pitting, the nails are very likely part of the same disease process.

Medications That Affect Nail Color

A number of prescription drugs can alter the way nails grow, sometimes producing white lines or bands as a side effect. Chemotherapy agents are the best-known offenders, as discussed above, but they are not alone. Retinoids, protease inhibitors like indinavir, and several other drug classes have been reported to cause nail abnormalities.⁹ The mechanism varies by drug. Some interfere directly with the matrix cells’ ability to produce properly keratinized nail plate; others affect blood supply to the nail bed.

If you notice new white lines appearing on multiple nails after starting a medication, it is worth documenting the timing and mentioning it at your next appointment. Drug-induced nail changes are generally reversible once the medication is stopped or adjusted, but because toenails grow so slowly, it can take the better part of a year before the affected nail fully grows out and is replaced by normal-looking nail.

Hereditary Leukonychia

In rare cases, the white nails are not caused by injury, infection, or disease but are simply inherited. Hereditary leukonychia produces milky white nails, sometimes called porcelain nails, that are present from birth or early childhood and persist throughout life. Researchers have traced this condition to mutations in the PLCD1 gene, which encodes an enzyme involved in how nail cells develop.¹⁰ The mutations reduce the enzyme’s activity, disrupting the normal process of nail formation enough to produce the uniform white appearance. The condition follows an autosomal dominant pattern, meaning a child needs only one copy of the variant from one parent to have white nails.¹¹

Hereditary leukonychia is benign. The nails look unusual but function normally. Because it is present from early life and affects all nails uniformly, it is usually easy to distinguish from acquired causes. If every nail on your hands and feet has been white for as long as you can remember and the same is true for a parent or sibling, genetics is the most likely explanation, and no treatment is needed.

A Simple Pressure Test You Can Do at Home

One of the most useful things you can do before deciding whether to see a doctor is press gently on the white area with a fingertip. If the whiteness disappears while you hold pressure and returns when you let go, the problem is in the nail bed, not the nail plate. That makes it an apparent leukonychia, the category that includes Muehrcke lines, Terry’s nails, and Lindsay’s nails. These are the types more commonly connected to systemic issues like low albumin or kidney disease.

If pressing does nothing and the white mark stays put, it is either embedded in the nail plate (true leukonychia) or sitting on the surface (pseudoleukonychia from a fungus). True leukonychia from minor trauma will grow forward and eventually reach the free edge. Fungal patches tend to spread laterally rather than migrate forward and may feel chalky or rough.

This pressure test is not a diagnosis, but it narrows the field enough to help you decide whether a visit to a dermatologist is worthwhile. A single white dot on one toenail that you can watch grow toward the tip is almost certainly a bump you’ve forgotten about. Multiple matching bands on several nails at the same level, or whiteness that covers most of the nail and responds to pressure, warrants a closer look.

When White Lines on Toenails Call for Medical Attention

Most white spots and lines on toenails are harmless and need no treatment. But certain red flags shift the picture:

• Multiple nails affected simultaneously: Matching bands at the same level on many nails suggest a systemic event, whether from medication, heavy metal exposure, or a period of severe illness.
• Spreading chalky patches: White areas that enlarge over weeks and feel rough on the surface suggest a fungal infection that will keep getting worse without treatment.
• Whiteness that covers most of the nail: Diffuse ground-glass whitening or a half-white, half-brown pattern, especially on multiple nails, can reflect kidney disease, liver disease, or heart failure.
• Accompanying symptoms: Fatigue, swelling in the legs, unexplained weight loss, or changes in urination alongside nail changes make a medical workup more urgent.
• Nail changes combined with skin plaques: If you also have scaly patches on your skin, elbows, or scalp, nail psoriasis becomes a strong possibility and benefits from coordinated treatment.

A dermatologist can use dermoscopy to examine the nail more closely, distinguishing surface fungal involvement from deeper matrix disruption without needing to remove the nail. If a fungal infection is suspected, a nail clipping can be sent for culture or microscopy. If the pattern suggests a systemic cause, blood work to check albumin, kidney function, and liver enzymes is a reasonable next step.

Why Toenails Show Problems More Than Fingernails

Toenails are particularly prone to white marks for a few compounding reasons. They endure more repetitive mechanical stress from walking, running, and being compressed inside shoes. They grow at roughly half the speed of fingernails, which means any disruption to the matrix stays visible for much longer. And the warm, moist environment inside shoes makes toenails far more vulnerable to fungal colonization than fingernails, which stay exposed to air most of the day.

This combination means that even a perfectly healthy person who exercises regularly or wears snug footwear will likely see a white spot or line on a toenail at some point. Athletes, hikers, and anyone who spends long hours on their feet in closed shoes are especially familiar with the phenomenon. If you are seeing occasional marks that grow out and are replaced by clear nail, your toenails are doing exactly what toenails do in response to everyday wear and tear.