Your annual mole check may be the only time you see a dermatologist, but skin doctors do a lot more than examine your body’s largest organ, remove suspicious moles, and remind you to wear sunscreen. We talked to a few to get an inside look at their profession, from how they can detect brain tumors to how they know if you’re lying to them about your daily skincare routine.

1. MAKEUP, TATTOOS, AND NAIL POLISH MAKE THEIR JOB HARDER.

When you see your dermatologist for an annual checkup, don’t wear makeup, nail polish, or hair extensions. Because dermatologists may look for skin cancer all over your body—under your toenails, on your scalp, and even on your eyelids—it’s important that you arrive at your appointment as close to your natural state as possible. (Even tattoos can make skin cancer harder to spot.)

2. THEY CAN DIAGNOSE MORE THAN SKIN CANCER …

When it comes to melanoma, physician Marla Klein tells mental_floss that dermatologists absolutely save lives: “If spotted early, treatment is simple. If it is detected late, it can metastasize, resulting in death in the span of a few years.”

But by looking at your skin, dermatologists may also notice other major signs of ill health. “If eyes are the windows to the soul, then skin is the window to your health. In my career thus far, I have diagnosed three rare brain tumors, simply with a detailed patient history and visual examination of their skin,” says Dr. Stuart H. Kaplan, a Beverly Hills dermatologist and UCLA Assistant Clinical Professor. Other doctors and dermatologists had written off the patient’s symptoms as being caused by genetics, but Kaplan’s years of experience allowed him to diagnose the underlying problem.

3. … AND DETECT OTHER HEALTH PROBLEMS EARLY.

Besides skin cancer and brain tumors, other health problems can reveal themselves on your skin, even before you experience other symptoms. According to dermatologist Albert E. “Bo” Rivera of Alabama’s Southeastern Skin Cancer & Dermatology, the skin is often the first place to show changes before a patient notices a problem and/or before a condition fully presents itself in blood tests. By examining your skin, a good dermatologist can detect systemic diseases such as diabetes, lupus, autoimmune conditions, thyroid abnormalities, and cholesterol abnormalities, saving a patient precious time, cost, and stress. 

4. THEY FEEL PRESSURE TO LOOK GOOD.

Dermatologist Terry P. Morris explained to Cosmopolitan the pressure that she feels to have flawless skin: “I have to try to look the best I can look. Because if I don't, how are patients going to believe that I can make them look better?” Morris explains that she and her staff have free reign to try products and treatments—creams, lasers, and Botox—so there’s no excuse for them not to look their best.

5. LIFESTYLE CHOICES CAN MAKE A BIG DIFFERENCE.

Although dermatologists use technology and prescription drugs to help heal your acne and smooth your skin, lifestyle choices can make a big difference. That’s why most dermatologists recommend that you do everything you can to achieve optimal health and wellness. Besides regularly wearing a broad-spectrum UVA and UVB sunscreen, dermatologists suggest that you get enough sleep, never smoke, exercise, wash your face, carefully remove makeup, and avoid high glycemic index foods (such as sugar and white bread).

6. THEY WISH PATIENTS UNDERSTOOD THAT LESS IS MORE. 

Most dermatologists see patients who struggle with a skin condition mistakenly overcompensate with a barrage of expensive products. Dermatologist Harold Lancer tells Everyday Health that “great, healthy skin requires a synergy of ingredients.” But patients should keep their skincare regimen simple to ensure that each medication does its job. Benzoyl peroxide, for instance, can cancel out a product with retinol—meaning that you shouldn’t put both products on your face at the same time. In addition, some patients buy expensive anti-aging creams and moisturizers under the false impression that more expensive products are always more effective. Often, cheaper products have the same ingredients and efficacy as the more expensive ones. 

7. THEY LOVE MAKING SKIN ANALOGIES.

To help patients have an “aha!” moment about their skincare, dermatologists make analogies. “I tell my patients to think of their skin like a plant; a plant cannot speak when it is hungry or needs to be moved away from the sun. You only know something is wrong with a plant when it shows wilted and yellowed leaves. So I educate my patients to pay attention to their skin and to look for warning signs, such as a funny looking mole or a cut that will not heal,” says Kaplan.

Similarly, dermatologist Tsippora Shainhouse reveals to Self that she uses a food analogy to encourage her patients to avoid tanning. “I tell my patients to consider their skin as white bread. Once you toast it, it will never be soft and white again, even if you never burn it,” she says. “Tanned skin equals damaged skin,” Shainhouse reiterates. 

8. THEY SOMETIMES PRESCRIBE SURPRISING DRUGS.

Don’t be surprised or think it’s a mistake if your dermatologist prescribes you a seemingly unrelated medication for your skin condition. Dermatologist Debra Jaliman tells The Oprah Magazine that she has prescribed antihistamines for rosacea, acne medication for keratosis pilaris, and Botox for migraines. Off-label prescription drugs are common in medicine, and dermatology is no exception. 

9. SEE THEM AFTER A FALL OR A FIGHT.

If you get in a fight or accidentally hurt yourself, consider seeing a dermatologist. According to dermatologist Fredric Brandt, specialists like him can treat bruises with a V-Beam vascular laser, which delivers short pulses of energy to dilated blood vessels. “It takes about 48 hours for a bruise to develop fully … the procedure takes only 20 seconds, and the bruise will fade by the end of the day,” Brandt says.

10. THEY KNOW IF YOU’RE LYING TO THEM. 

If you think you can pick your skin or pop your pimples without your dermatologist being the wiser, think again. Redness, scabs, and scars can give away your secret picking and popping, so don’t bother lying to your dermatologist. And tell them the truth about your sunscreen and tanning habits. “Dermatologists know when you went out without your sunscreen. Your normal, natural color is what is not usually exposed in the sun, so typically the buttocks is a good comparison. We're not upset with you but want to educate you so that you don't have problems arise in the future,” Rivera tells mental_floss.

11. THEY DON’T ALWAYS WEAR SUNSCREEN. 

Although the most important way to protect your skin is to wear sunscreen, dermatologists don’t always heed their own advice. Jaliman says that she used to walk her dog for five minutes each morning, sans sunscreen. But after noticing freckles beginning to appear on her face, she decided to change her ways. Because minute exposure to the sun adds up over time, she now follows her own advice and always wears sunscreen, no matter what.

All images courtesy of iStock