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Your skin is your largest organ—and unlike your heart or lungs or kidneys, you can actually see it. That makes it a useful window into what’s going on inside your body. “It’s an immediate indicator of potential internal health concerns,” says Dr. Amy Basile, a dermatologist at Dermatology Partners in Philadelphia, starting on day one of life: If a baby’s skin is jaundiced, for example, doctors know to look for high levels of bilirubin or an immature liver. Throughout the years that follow, the skin continues to provide clues about underlying health concerns, from cancer to autoimmune disease.
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It’s key, however, to know what to look for. Not every blemish is a marker of internal turmoil, but certain ones raise red flags for dermatologists, who then investigate further. We asked skin doctors to share the weird or surprising symptoms that make them take notice.
A bleeding acne-like bump
Dr. Rina Weimann constantly sees patients who come in complaining about a solitary, stubborn bump they’ve had on their nose or face for a few months. “It looks like a pimple, but it doesn’t have a head,” says Weimann, a dermatologist at Schweiger Dermatology Group and assistant professor of dermatology at Drexel College of Medicine. “It’s like a shiny pink bump, and it bleeds without you touching it.” Having that kind of growth linger for so long isn’t normal, she adds, and warrants a biopsy to ensure it’s not skin cancer.
Biopsies aren’t as scary as they might sound: Typically, dermatologists remove a small sliver of your skin and send it to a pathologist. It takes about one or two weeks to get results, Weimann says. And if you do have skin cancer, “it doesn’t mean you have to have your nose cut off,” she says. “Especially on the face, we do a specialized surgery called Mohs surgery to conserve tissues, so you’re not taking a ton of skin out.”
Sudden changes in body odor
Dr. Angela Brimhall still remembers the stench she encountered during her dermatology residency, when she stepped off the elevator at the hospital. Down the hall, a patient was suffering from severe gangrene, “and the odor that it puts off is very unique and telling,” she says. While not always so noxious, Brimhall often sees patients with odor-related symptoms, which can indicate a range of hormonal issues or infections.
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While gangrene causes a foul, musty odor, for example, “Staph and strep have been described as having a mildly sweet smell—but like if something sweet is turning sour,” says Brimhall, a dermatologist at Sage Dermatology & Mohs Surgery in Draper, Utah. A metabolic disorder called trimethylaminuria, meanwhile, makes your sweat smell like rotten fish. Some people experience it episodically, like at the start of menstruation, and dietary tweaks can help relieve it; other times, antibiotics are necessary. “You don’t have to suffer with it forever,” she says, but first you need a doctor’s help to figure out what’s going on. “Your skin is a dynamic organ, and it’s communicating with you, telling you what’s going on inside.”
Visible veins or blood vessels
If your veins suddenly take on a starring role on the canvas that is your skin, call your doctor—especially if the newfound prominence is accompanied by swelling, pain, or redness. “If they were previously just minding their own business, and you couldn’t see them, that could indicate deep vein thrombosis,” Brimhall says. “It can also happen with some autoimmune diseases.”
Factors like vigorous exercise, hot weather, sun exposure, and tight clothing can also make your veins more noticeable, which is why it’s important to have your doctor take a look and determine the seriousness of the situation.
Blue discoloration of the skin
Any change in skin color, especially if it’s widespread or worsening, warrants a doctor’s appointment. Blue discoloration often ends up being related to a medication or supplement someone is taking, Basile says. Supplements with silver, for example, can cause a difficult-to-treat condition called argyria that turns the skin bluish-gray, while the antibiotic minocycline can cause the same discoloration on the arm, face, and shins. If you go out in the sun without protection while taking the arthritis drug Plaquenil, you could end up with blue-gray arms and feet, Basile adds. Usually, when that happens, “you stop the medication and find an alternative,” she says. “In some cases, it goes away, and other times, these pigmentations need to be removed with lasers,” which can be time-consuming and expensive.
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A blue tinge to the skin might also signal someone is taking kratom, an herbal supplement that can have opioid- and stimulant-like effects. Sometimes, people taking kratom develop gray-blue hyperpigmentation in areas that are exposed to the sun. “You have to really pry and say, ‘Are you taking any new teas? Are you adding anything to your orange juice? Are you taking any new vitamins?’” Basile says. “These things come in so many forms, and they’re not regulated,” which is why she encourages her patients to avoid kratom.
Changes in nail appearance
Your fingernails are “an excellent place to see how your body is doing metabolically,” Brimhall says. Discoloration, ridges, and splitting nails can all reflect systemic health issues.
Splinter hemorrhages, for example—or squiggly red lines under the nails—can indicate a heart infection called endocarditis. “You’re throwing little bacterial-originated clots into the bloodstream, and the capillaries of the nails are superficial enough and small enough that they’re picking up those clots, and you can see them, like a window, right there around the nails,” she says.
You might also notice signs of potential autoimmune disease. For example, tiny red or white spots around your nail bed—called periungual telangiectasias, or small, dilated blood vessels—can point to dermatomyositis or lupus. Meanwhile, if you experience “spooning of the nails,” which means they curve inward and take on a spoon-like shape, you might be experiencing hypothyroidism or anemia, Brimhall says. “Clubbing” of the nails, on the other hand, which refers to a widening and rounding of the fingertips and toenails, often clues doctors into inflammatory bowel disease or pulmonary issues.
It’s also important to keep an eye out for a dark line that runs from the top to bottom of your nail. This type of discoloration is most prevalent in the thumb, index finger, and big toe, Basile says, and can indicate melanoma of the nail. Basile generally measures the line, and if it gets wider or becomes irregular at the base, recommends her patients get biopsied.
Velvety skin
If you have thick, darkened patches of skin on your neck, armpits, or groin that feel soft and smooth, you might have a condition called acanthosis nigricans. “Patients often come in because they don’t like it,” Basile says. “They’re like, ‘What is this?’” Unfortunately, “it’s very difficult to treat with topicals.”
Acanthosis nigricans is often caused by insulin resistance, which can lead to Type 2 diabetes if not addressed. Basile urges patients to take it seriously—especially adolescents who are overweight and going through puberty. “It may be the first indicator that your body isn’t responding effectively to insulin,” Basile says. “It’s like your first chance to address that, and to motivate yourself to make lifestyle changes and enhance your diet and exercise habits.”
Skin that glows or shines
Glowy skin is in right now. But a sudden, unnatural sheen could indicate hormonal changes, skin infections, or even cancer. “When I’m doing a full-body skin exam, I’m looking for a certain sheen that can be consistent with basal cell carcinoma,” Brimhall says. “It’s often described as a pearly appearance, and we’ll see it right over the area that’s having [abnormal cell growth]. That can be a big clue that something concerning is going on.”
Basal cell carcinoma—which is highly curable when identified and treated early—usually develops in areas exposed to sunlight, like the face, head, neck, arms, and legs. You may notice tiny blood vessels on the surface of a translucent bump, and it may eventually bleed or scab over.
Itchy palms
Your hands might very well become itchy during the long, cold winter because they’re dry. But if you’ve been persistently overcome with the urge to itch for months, it’s time to get curious—especially if the itchiness flares up at night and isn’t accompanied by a rash. “That could be a sign that you need to do blood work to check your liver function and bile acid, and make sure there’s not an issue with your gallbladder,” Weimann says. “It’s important not to ignore.” She usually refers patients with itchy palms to a hepatologist or their primary care provider for additional testing.
A slow-healing wound
Maybe you’ve been diligently taking care of a wound on your leg for months, applying Vaseline or Neosporin, and it’s not going away. Some people are simply slow healers. “But it does make me concerned: ‘Should I do a biopsy and investigate this for skin cancer?’” Weimann says. “A lot of dermatologists will do that for slow-healing wounds.”
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Squamous cell carcinoma, in particular, can show up as a wound that refuses to heal—in addition to symptoms like a firm, dome-shaped growth, or a sore that develops in an old scar. The earlier you start treatment, the better, so if you’re worried, call your doctor.
Skin that feels like sandpaper
If your skin becomes so dry that it starts to resemble sandpaper—laden with small, rough bumps—you could have a condition like keratosis pilaris, also known as “chicken skin.” It’s characterized by “these tiny little 1-millimeter bumps that are very close together,” Brimhall says. They’re particularly common on the upper arms, thighs, and butt, and while the bumps are typically painless—and can be treated with moisturizers and prescription creams—they’re sometimes a harbinger of more serious afflictions.
“We know that if you have keratosis pilaris, you’re predisposed to atopic dermatitis, asthma, and seasonal allergies,” Brimhall says. “We want to make sure we’re watching for any of those signs and symptoms, so if they develop, we’re really on it.”
Unexplained hair changes
If you notice sudden graying or other changes to your mane, call your doctor instead of your hair stylist. You could be dealing with an underlying health issue or nutritional deficiency. “Sometimes when the body goes into survival mode, it’ll show up in changes in your hair, and that can include color change or hair loss,” Brimhall says. The autoimmune condition alopecia, for example, can cause hair to turn white or gray, before ultimately leading to bald patches. Another autoimmune condition, vitiligo, causes loss of skin pigment, which can show up as white or gray hair. In rare cases, melanoma can also lead to these changes, usually darkening the hair in the affected area. “It’s important to pay attention,” Brimhall says, “because your hair can indicate something deeper is going on.”
Increased sensitivity to products that didn’t previously cause issues
If you start to experience sensitivity in the area where you’re applying a certain product, you might have allergic or irritant contact dermatitis. On average, it takes five years to develop a topical allergy, Brimhall says. “Sometimes patients will say, ‘I’ve been using this for years,’ and we’ll say, ‘Well, we still need to do a patch test,’” she adds. “The other difficult thing about these conditions is it’s often a delayed hypersensitivity—so you’ll put the product on, and the rash doesn’t appear for five to 10 days.” It might then linger for weeks or months.
Brimhall often asks patients to make a list of products they were in contact with, even briefly, like the bar of soap they used while staying at a hotel a month prior. Then, she instructs them to eliminate all of their products, adding one back in at a time and, after two weeks, adding another. “That way we can really see what’s affecting your skin,” she says. It’s a painstaking process, but “the upside is, once we identify the chemical that’s causing this reaction, we have a 100% cure—and that’s 100% avoidance.”
