As if equipped with X-ray vision and psychic abilities, dermatologists know an astonishing amount about your health after a single glance in your direction. In fact, even before learning your reason for visiting, a dermatologist likely has a few ideas about what’s going wrong and how you should be treated. Conditions you could be completely unaware of catch a dermatologist’s trained eye the second you walk through the door.

“I immediately notice the quality of the skin and hair, which gives me tremendous insight into the patient’s diet and stress levels,” says Whitney Bowe, MD, a board-certified Dermatologist in New York City.

The first thing they’ll notice is “whether the patient has a deep frown line. Typically, the skin is at the very least dehydrated, dull, and with a little bit of laxity. It’s a good reminder to use a medical-grade skin care line like NeoCutis, which has a number of active ingredients to help stimulate cell turnover and restore hydration to the skin,” says Ava Shamban, MD, Beverly Hills Dermatologist and founder of SKINxFIVE.

“The next step would be to identify if the patient has acne or rosacea, and how many superficial line wrinkles versus deeper lines and wrinkles there are,” Dr. Shamban adds. (Here are a few important things everyone needs to know about rosacea.)

However, beyond noting the strengths and shortcomings of your skin-care routine, your dermatologist can also tell a ton about your body’s general well-being just by looking at your skin. “The skin is a window to our overall health. Not only can it show signs of an underlying medical condition (such as a thyroid issue, autoimmune disease, or even diabetes), it also reflects your overall diet, stress levels, and hormonal balance,” Dr. Bowe says.