You probably think of your skin as only external, but there’s a lot that goes on below the surface that your skin can reveal. “As the largest organ of the human body, skin can serve as an important window to internal health,” says Jameelah Gater, M.D., an integrative family medicine physician. “Changes in skin appearance can signal internal imbalances in digestion, hormones, immune function, blood sugar, and inflammation.”
In fact, everything from dullness to discoloration from your usual tone can signify that something is going on with your health—and, in many cases, skin changes can actually be the very first clues that you’ve got some digging to do. “Healthy skin is not just a reflection of beauty; it is also a reflection of overall health and wellness,” Gater notes. Similarly, skin-care is truly so much more than face masks and body scrubs but investigating possible health concerns (from food intolerances to too much stress) and how they could be affecting your skin, too.
Here are some possible hints toward what may be happening in the rest of your body, based on what’s going on with your skin.
1. You’re dehydrated
“Even dehydration can be detected via skin changes,” Gater says. While a one-time instance of dehydration might leave you with a headache, dry mouth, or muscle cramping, chronic dehydration also often causes skin dullness and itchiness.
To get a better sense of how hydrated you (and your skin) are, Gater recommends the skin pinch test. “If it takes more than one to two seconds for skin to snap back after being pinched, that can signal dehydration.”
To support full-body hydration and bouncier, brighter, less-itchy skin, many experts recommend dividing your weight in half and shooting for that many ounces of water per day. (So if you weigh 150 pounds, that’s 75 ounces of water per day.)
2. You have an autoimmune condition
Joint pain and digestive issues can be two of many other signs of an autoimmune condition that many people experience, but your skin can also alert you of one. A butterfly-shaped rash across your cheeks and nose, for example, might be a sign of lupus or autoimmune skin conditions like rosacea or eczema, suggests Gater.
Diagnosing autoimmune conditions can be challenging—and might require multiple panels of tests and visits to more than one doctor or specialist. That said, for something like eczema that mainly affects the skin, a dermatologist can prescribe you a topical medication or an immunosuppressant steroid (in severe cases). For rosacea, a derm might prescribe specific creams and cleansers, and recommend applying sunscreen daily to prevent redness and irritation from the sun.
3. You have a thyroid issue
Pay close attention to your skin, as well as your hair health and nail health, if you suspect you might have a thyroid condition. Hypothyroidism (a.k.a. underactive thyroid) is often characterized by weight gain, tiredness, and sensitivity to the cold, as well as dry, coarse-looking skin, according to Gater. (You might notice hair loss and brittle nails that have visible ridges, as well.)
If you notice any of these changes, check in with your healthcare provider as soon as possible, Gater recommends.
4. You’re eating too much sugar
We wouldn’t dare suggest you give up chocolate—but eating too much sugar does wear on your skin over time. “When we eat sugar, it damages the collagen in our body, which then causes our skin to look dull and saggy,” explains dietitian Lauren Pimentel, R.D. Not to mention, loading up on sugar can exacerbate pre-existing inflammation, which could be problematic if you already have an inflammatory skin condition like rosacea, psoriasis, or acne, she notes.
High-glycemic foods, such as ice cream, cookies, and French fries, which cause your blood sugar to spike and then drop, are particularly pesky because blood sugar spikes trigger both inflammation and oil production, both of which contribute to acne, Pimentel says.
If you notice an increase in breakouts or dull-looking skin after eating many of these foods on a regular basis, consider it a sign that you need to reevaluate your sugar intake. Pimentel suggests steering most of your eats towards lower glycemic foods (think fruits and veggies, lean protein, brown rice, and natural nut butters) and enjoying higher glycemic foods more sparsely.
5. You’re overly stressed
Excessive stress is lethal for your skin. Like sugar, stress triggers inflammation, meaning that it can worsen acne or cause psoriasis or eczema flare-ups. “Stress also can cause shifts in levels of the hormone cortisol, which increases oil production,” Gater says.
One way to get a handle on stress is to revisit your sleep schedule. Gater recommends making sure you’re consistently sleeping eight hours a night so that your body can naturally rejuvenate, manage cortisol levels, and repair and replenish your skin.
6. You have a food allergy or intolerance
While certain (and severe) food allergies cause an unmistakable acute reaction, subtler food intolerances may have a sneakier impact on your body—and may even show up on your skin.
“Certain foods can trigger an inflammatory response in the body, leading to conditions such as acne and rosacea,” Pimentel says. One common intolerance is sensitivity to lactose (or dairy in general), which may show up as breakouts that gather near your forehead and chin, she suggests. Gluten is another common one.
If you suspect dairy may be an issue for you, “try replacing your usual dairy with dairy-free alternatives, such as coconut or almond milk, and see if your skin condition improves,” Pimentel suggests. To better understand your genetic risk for inflammatory skin conditions and certain food allergies and intolerances, Gater suggests trying an at-home DNA test (like 23andMe).
7. You could have celiac disease
Beyond just an intolerance to gluten, celiac disease, a condition in which the immune system responds to gluten by damaging the small intestine, can certainly show up on your skin.
Sometimes, a cluster of random bumps, blisters, or a rash on the skin could be a sneaky sign of celiac, explains dietitian Tayler Silfverduk, R.D.N. “Some people with celiac experience a rash known as Celiac Dermatitis Herpetiformis, which presents similarly to herpes or eczema after eating gluten,” she notes.
Since celiac disease is a serious condition that often requires more medical attention than just eliminating gluten from your diet, schedule a check-in with a dermatologist if you notice a rash or any blistering, Silfverduk recommends.
8. You’re deficient in iron
Here’s another one you might not be on the lookout for (unless, of course, you already have symptoms of iron deficiency anemia, like consistently cold extremities and fatigue). Because iron is needed to produce red blood cells—which deliver oxygen to cells, tissues, and organs—a deficiency in iron can affect any organ in your body. Your skin often takes a noticeable hit, with those deficient in iron noticing paleness and dark circles under their eyes, explains Pimentel.
Want to up your iron levels? Red meat is not your only option (though lean beef, along with other animal proteins, including chicken, turkey, and tuna, are key sources of iron), says Pimentel. You can also get plenty of iron from plant-based foods, like tofu, lentils, beans, cashews, spinach, and potatoes, she says. Iron supplementation is also an option.
Plant foods that contain vitamin C, like oranges, kiwi, and broccoli, can help your body better absorb iron, Pimentel adds. Plus, good ol’ C on its own is an important nutrient for supporting your skin, so pairing it with your iron-containing foods is a win-win.