When something is off with your skin, the signs are often obvious, meaning that you can both feel and see them. For example, you've learned to spot a potential breakout before it happens, you can feel your cheeks flush during a rosacea flare-up, and you can visibly recognize dry skin as it flakes off. Our nails, however, also hold clues about our overall health — though they're often either covered in nail polish or overlooked altogether.
"Nails are made up of keratin, which is the same material in your skin and hair," explains Gary Goldenberg, a board-certified dermatologist in New York City. "In the nail, the keratin is more compact and has multiple layers, which is what makes the surface hard, offering protection to the nail bed." This similarity in structure is important because just as your skin can offer clues about your health, so can your nails.
"The nails are a dermatologist's dream to see inside some of the body's ailments," says Ellen Marmur, a board-certified dermatologist in New York City. "Unhealthy looking nails may be able to tell you about a bigger issue with your overall health."
To find out more, we spoke with experts about how the appearance of your nails can offer clues — in some cases, serious ones — about the state of your overall health. Here are the five top warning signs to look out for with regard to nail health.
1. A white half-moon at the base of your nail
The technical term for this is lunula, and "a normal lunula or moon shape is small, just peeking out from your cuticle," Marmur explains. If you have a little bit of white poking out, it's not at all cause for concern. In healthy nails, "they are a whitish color and take up a small portion of the bottom of your nail," explains Carielle Nikkel, a registered dietician and nutritionist.
However, if the white portion of the nail grows and begins to take over half of your nail or more, then it becomes a different story. "This is called Terry's nails, [and it's] an indication of systemic illnesses from liver disease to heart failure," says Marmur.
This is different from a tiny white line that may appear toward the bottom of the nail bed and work its way upward — that can simply be caused by physical damage to the nail bed. In a case of Terry’s nails, however, half or more of the entire nail will appear white.
2. Brittle, weak nails
As with many things pertaining to health, this could be caused by a variety of different things — ranging from feelings of stress, over-consumption of alcohol, general aging, and vitamin deficiencies. It is most often seen, however, "in patients with poor nutrition," Goldenberg says.
Some of the most common vitamin deficiencies that can contribute to brittle, weak nails include B vitamins (including biotin), vitamin D, and iron. "Brittle, weak, and dry nails are often caused by iron deficiency," Nikkel says. "While a leading sign of iron deficiency is fatigue, it can also manifest through brittle or spoon-shaped nails."
Perhaps the next most common culprit of weak nails: stress. "When your body is under stress, it has limited supplies of nutrients, which are sent to vital organs, such as your brain and heart, and [taken] away from 'less important' places, like your hair and nails," Goldenberg explains.
3. Black or brown streaks
Out of all of the abnormal nail signs to keep an eye out for, this is perhaps the most important. "The number one nail-health emergency is a brown stripe that starts on your cuticle," Marmur says.
This is called melanonychia, which is technically defined as a black or brown pigmented streak on the nail bed, Goldenberg explains. In most cases it is benign, however, in some circumstances, it can actually be a sign of melanoma, the most lethal form of skin cancer, "which can be dangerous or even life-threatening, since it is a cancerous lesion," Goldenberg explains.
If you notice a brown line forming in your nail bed — it usually presents itself vertically — then it's wise to make an appointment to consult with your dermatologist right away.
4. Horizontal ridges
Horizontal rows of raised ridges on the nail itself — not the underlying nail bed — can be caused by trauma to the nail itself, Marmur explains, but they can also be a sign of something more serious.
Aside from physical trauma to the nailbed (such as slamming your finger in the car door, for example), horizontal ridges "can also indicate malnutrition, psoriasis, or a thyroid problem," Marmur explains. "Check with your doctor if you see horizontal ridges on your nails; they may indicate a more serious problem."
5. A red-colored infection
"The nail and fingertip are a closed compartment, so if it gets too swollen or infected, it can cut off circulation," Marmur explains. If you find that your nails or a singular nail is red, swollen, and infected, Marmur recommends heading to the emergency room right away.
The Bottom Line
"The skin is your body's largest and most visible organ, always giving clues about your health," Marmur explains. "When your skin is unhealthy, your nail matrix is compromised and forms an unhealthy nail. Conversely, when you take good care of your body, your skin and nails will be healthier."
If you notice any changes to your nail bed or nails, don't get stuck down a scary internet rabbit hole. Instead, visit a board-certified dermatologist who can rule out more serious health conditions and advise on best practices for the future.
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Originally Appeared on Allure