Seeing a skin doctor isn’t just about checking for moles or getting a cream for acne or wrinkles. Dermatologists may see early signs of everything from celiac diseases to diabetes.

By Lauren Gelman

Your next dermatologist visit could reveal important health information that’s more than skin deep.

Some 30 to 40 percent of issues dermatologists see may be related to underlying chronic conditions, estimates Lisa Grandinetti, MD, assistant professor of dermatology at the University of Pittsburgh Medical Center. “Skin is the window to your health,” says Wilma Bergfeld, MD, senior dermatologist in the department of dermatology in the Cleveland Clinic. Medical dermatologists are seeing more and more skin issues especially related to immune system problems, including lupus, rheumatoid arthritis, and inflammatory bowel disease. In many cases, dermatologists might help discover conditions during routine visits—before a specialist would—which can ensure patients get treated in earlier stages of illness. Here are some important conditions your skin doctor has her eyes on. (For more details on what any of the rashes or skin issues named in this piece look like, we highly recommend looking at Google Images).

Diabetes

Diabetes is very common—almost 10 percent of Americans have it. Dr. Grandinetti estimates that about half have some kind of skin disease. The main one is called acanthosis nigricans, a velvety thickening of the skin that occurs around the neck and in the underarms. Usually patients with these dark patches don’t know they have diabetes when we see them, says Dr. Bergfeld. “In dermatology, they tend to be younger, so we pick up these cases early.” Skin tags are another sign, but they’re not an automatic red flag. “Everybody gets skin tags under their arms every now and then, or in the groin area just from rubbing,” says Dr. Grandinetti. “If somebody has no other risk factors for diabetes—they aren’t overweight, there’s no family history, and they only have one or two skin tags, there’s really no evidence to support further testing. But if someone has multiple skin tags around the neck, in the underarms, and in the groin and they also have acanthosis nigricans, then I usually test their blood glucose levels or A1C levels.”

Celiac disease

Super itchy clusters of blisters called dermatitis herpetiformis, which commonly occur on the elbows, knees, buttocks, and sometimes the scalp, are a clear sign of one disease: celiac. “If you have this condition, you have celiac, although not everyone with celiac will have dermatitis herpetiformis,” says Dr. Grandinetti. She says patients who have this skin issue who don’t have any GI concerns are often shocked to learn they have celiac. And when they begin a diet free of gluten—the protein found in wheat, rye, and barley that triggers an immune system response in celiac patients—their skin gets better too.

Rheumatoid arthritis

This inflammatory disease, which causes swelling and pain in the small joints of the hands and feet, can sometimes manifest in the skin. About 20 to 30 percent of RA patients can get subcutaneous (beneath the skin) lumps near an affected joint, according to Johns Hopkins Arthritis Center. “Thinning of the skin, translucency of the skin on the back of the hands or brittle nails may also be common signs of rheumatoid arthritis,” says Roshini Raj, MD, assistant professor of medicine at the NYU School of Medicine and co-founder of TULA skin care.

Lupus

A sunburn-like rash across the top of the cheeks is often an important clue for lupus, an inflammatory disease in which your immune system attacks the body’s tissues and organs. Patients with lupus may also have a red rash on their scalp and on areas of their skin that get a lot of sun exposure, such as the neck, the backs of the arms, and the upper back. Anywhere from 40 to 70 percent of lupus patients can find that sun exposure makes their disease worse, according to Lupus.org.

Thyroid disease

Chronic hives—those that last longer than six weeks—could be a sign of thyroid conditions like Graves’ disease or Hashimoto’s thyroiditis, says Dr. Grandinetti. Doctors aren’t sure why these conditions trigger hives, but suspect that the body develops antibodies against certain parts of the immune system called IgE receptors, which triggers the allergic reaction.

Inflammatory bowel disease (Crohn’s and colitis)

Skin issues affect up to a third of patients with ulcerative colitis and up to half of patients with Crohn’s disease, according to a paper from researchers at Mt. Sinai School of Medicine and Columbia University College of Physicians and Surgeons. With cutaneous Crohn’s disease, for example, people can get fissures and nodules on the skin. “When we biopsy them, they almost really mimic under the microscope what Crohn’s disease looks like in the gut,” Dr. Grandinetti explains. Another sign more common in colitis patients is something called pyoderma gangrenosum—ulcer-like lesions that tend to occur on the shins, ankles, and arms. According to the Crohn’s & Colitis Foundation of America, they typically start as small blisters, but merge to become deep ulcers. Many IBD-related skin conditions ebb and flow with disease flare-ups; when your GI tract acts up, so will your skin.

Hepatitis C

About 15 to 20 percent of patients with this liver disease have symptoms that occur in their skin, according to research from Rutgers New Jersey Medical School. These include rashes like vasculitis and lichen planus—which each have very distinctive looks and patterns. “A lot of people who have hepatitis C don’t know that they have it,” says Dr.Gandinetti. “And so when people come in with lichen planus, part of my workup is to make sure I’ve checked them for hepatitis.”

Adrenal insufficiency

The adrenal glands—located just above the kidneys—are responsible for pumping out cortisol, a crucial hormone that helps the body respond to stress. Addison’s disease results when the adrenal glands don’t make enough cortisol, which can cause a diverse range of symptoms including muscle weakness and fatigue, weight loss and decreased appetite, low blood pressure and blood sugar, and more. Because symptoms of Addison’s disease can come on gradually and subtly, it’s often not diagnosed right away. One Addison’s symptom that’s a red flag for dermatologists is darkening of the skin; Dr. Bergfeld says it’s almost as if patients appear tan. Unexplained stretch marks in the skin are another sign.

Nutritional deficiency

“When patients come with hair loss or hair shedding, the most common triggers in women are nutritional and hormonal,” says Dr. Bergfeld. “When patients are on very restricted diets—they don’t eat any carbs, or they don’t eat any meat at all—they can have deficiencies in protein, zinc, vitamin D, and iron.” Other triggers for hair loss are hormonal problems such as androgen excess, in which an abundance of male hormones can cause a number of side effects, including hair loss on the head as well as increased body hair and acne.

Originally published on Reader’s Digest