It’s just a toenail, right? An important accessory you can choose to paint pink or teal, right? Nope. As it turns out, fingernails and toenails can give you some good hints as to the internal events of your body. While none of these clues are diagnostic of a specific disease, your fingernails and toenails can say quite a few things about your overall health.
From discolored toenails to strange lines and ridges, these are some of the most common ways your nails can indicate an underlying health concern.
White discolored nails
Referred to as onycholysis, this is a white discoloration that spreads down along the nail plate. If you look closely, you can see that the nail plate (top area) has separated from the nail bed (skin underneath). We often see this with trauma or fungal infections, though it can sometimes be related to hyperthyroidism.
An example I think of is when you run into something and it gets underneath your nail and hurts initially. Then later, you notice that instead of a thin white line at the top, there is a larger white area just where you were injured. There is no treatment for this unless there is an underlying condition to evaluate.
Clubbing is thickening of the tissue near the lunula (the white area at the base of your nail) and it looks puffy, rather than dented in as a diamond shape. Turn your finger sideways to see this. Clubbing could indicate many things, but pulmonary diseases like lung cancer or COPD, as well as inflammatory bowel disease, are classic examples of associated conditions.
Koilonychia is the fancy name for “spoon-shaped” nails and is most commonly seen in people who have anemia (common condition related to iron deficiency) or hemochromatosis (a more rare disease). We see this most commonly with iron deficiency, whether it leads to anemia or not. The nail does not lean outward as expected, but instead, dents in with a spoon shape.
If you notice your nails looking like this, talk to your doctor about checking your CBC (complete blood count) to look for anemia. A caveat to remember: don’t stress if your baby’s fingernails look this way. It can be normal for infants, but consult your pediatrician.
Horizontal white lines
If you notice white lines going across your nail bed horizontally, these are called Muehrcke lines. They can indicate low levels of albumin (a protein in the blood) and may require further blood work up. These lines do not grow out as your nail grows because they are in the nail bed underneath, not the nail plate. If the lines are due to low albumin levels, then as you correct and increase protein levels, they will begin to resolve.
Another common way you might see white horizontal lines appear are across the nail plate (not the nail bed like Muehrcke’s lines above). Called Beau’s lines, these can indicate that you have suffered from a severe illness or trauma that interrupted normal nail growth.
Since normal nails grow from lower on the finger, out the fingertips at a pace of about 1mm every six to 10 days, you can estimate the time of an illness or injury by looking at the lines. For example, say you had a severe illness and were hospitalized in the ICU for two weeks, you can probably see the white line of nail growth interruption that coincides with that severe illness timeframe. You’re welcome for this awesome party trick.
These are superficial indentations in the nail plate which can sometimes indicate psoriasis, although pitting can be associated with other conditions, including several autoimmune diseases and connective tissue disorders like arthritis.
Red or brown streaks
Splinter hemorrhages are red or brown little streaks that typically run vertically under the nails. Like several of these nail findings, these streaks can indicate several different things about your health. However, if this is a new finding along with a new heart murmur and a fever, then it is a red flag for endocarditis — an infection of the heart valves. Consult with your primary care doctor as soon as possible.
Long dark vertical lines
Called longitudinal melanonychia, this is a very common normal variant in darker skin pigments. The normal variant usually starts in the age range of 20s to 30s and in darker-skinned people. However, if these lines appear after age 60, then this is a major red flag and needs to be evaluated for possible melanoma (see below). Even in younger people, this benign condition can be difficult to distinguish from melanoma and should be evaluated by a dermatologist.
Subungual melanoma is a form of skin cancer under your fingernail. It accounts for half of melanomas in dark-skinned patients and if there is any concern, you should talk to your doctor. They may want to do a biopsy, which means taking a small sample and sending it to be looked at under the microscope by a pathologist.
Other red flags that can follow with melanoma: if you have discoloration of the nail and the underlying skin and disrupted nail growth, then this needs a biopsy to evaluate for melanoma.
Red growing mass on your nail
Squamous cell carcinoma is also a form of skin cancer, but different from melanoma. Squamous cell under the nail is typically more of a red, erosive, growing mass that disrupts the nail growth. Similar to melanoma, you’ll need to see a dermatologist for biopsy of this promptly.
Inflammation in the nail fold
If you notice sudden inflammation, or redness and swelling, of fingers or toes in the nail fold, it could be paronychia. This is most commonly caused by bacteria and will be red, warm and tender. You’ll need antibiotics and sometimes incision and drainage. Please don’t drain these at home — it usually leads to bigger problems as the risk of infection is much higher.
Chronic (ongoing) paronychia is seen more often in dishwashers, housekeepers and swimmers. Think about folks who are chronically using chemicals or frequently submerged in water.
Ragged or crumbly nails
You’re probably already familiar with onychomycosis. It’s the technical term for a fungal nail infection of the toenail unit (the plate, the bed and/or the matrix). Typically, it causes shape and color changes to the nail which you may notice as thickening of the tissue under the nail with flaking debris along the area.
Sometimes it’s just cosmetic but you may also notice pain or discomfort. This can be treated with antifungals, but keep in mind these do not always work completely. It can take between three and six months for your toenails to completely grow out and start fresh.
Ingrown nails, or onychocryptosis, often from trauma or improper trimming of the nails. The edge of the skin starts to grow over the edges of the nail plate, leading to significant pain and discomfort, and sometimes infection. There are some mild techniques we can use to help train the skin and nail to grow correctly, but sometimes your doctor will need to remove the ingrowing piece of the nail.
Blood under your nail
Subungual hematoma is a collection of blood under the nail, typically caused by trauma (like slamming a finger in a door or missing the nail with your hammer). The severity of these can vary — is it a small hammer with a light touch? Or are we talking about Thor’s hammer slamming down on your thumb? In mild cases, your nail may grow out and fall off with time. However, severe subungual hematomas can be quite painful and need to be drained by your doctor. If Thor’s hammer came down, you need to get an X-ray before anything gets drained.
If you notice any of these unusual clues in your own nails, don’t panic. Changes to your nails are not always an indication of a health condition. But if you’re worried, talk to your doctor — your nails could be trying to tell you something.
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About the author
Kathryn Greiner, MD, is a family medicine physician on the medical staff at Baylor Scott & White Clinic – College Station University Drive. She attended medical school and completed her residency at Texas A&M Science Center College of Medicine. Dr. Greiner enjoys teaching her patients how to partner with her for a healthier life. She is married with three children.