In order to understand the ins and outs of proper face washing, we turned to an expert on the matter: Dr. Dendy Engelman, a board-certified dermatologist in New York City who specializes in aesthetic medicine and Mohs micrographic skin cancer surgery. Here, Dr. Engelman reveals exactly what people should—and shouldn’t—do to their faces every morning and night.

What’s the first step to washing your face well?

Start with an oil-based cleanser, which works to eliminate impurities without drying out the skin, instructs Dr. Engelman. (She recommends Elizabeth Arden’s Ceramide Oil Cleanser, $36; amazon.com). “Essentially the oil binds to the oils on your face and the cleanser rinses them away, without stripping your skin of its good natural oils,” she explains. If your skin is oil-prone, Dr. Engelman suggests Epionce Gel Cleanser ($40; dermstore.com) to remove makeup and grime.

How essential are facial exfoliants?

Exfoliants are absolutely essential, says Dr. Engelman, because they will remove dead skin cells and flaky skin that can make your complexion look dull. She tells her patients to use a chemical exfoliant over physical ones.

How long you should physically wash your face before rinsing?

“As long as it takes to thoroughly remove makeup,” Dr. Engelman says. That ends up being about a one- to two-minute process. To maximize your efforts, she suggests moving in circular motions as you cleanse. “Besides makeup, there are many environmental aggressors, like pollution and bacteria, which can cause rapid aging if left on the skin,” she adds. “It is important to wash these impurities away as well.”

What skincare ingredients should be avoided?

Definitely avoid Triclosan, says Dr. Engelman. “This ingredient is used to reduce bacteria in products, and it’s added to soaps and washes, and even some clothing and cookware,” she says. “It has been linked to skin cancer and thyroid issues.” Another ingredient to stay away from is sodium lauryl sulfate, a chemical that acts as a foaming agent in many soaps and washes. “The level of concentration of this chemical is too irritating by cosmetic standards,” Dr. Engelman says. “Our bodies are not able to break this chemical down, and with prolonged exposure, it can cause issues with the nervous system and kidney and liver function.”

How often should you really wash your face?

At the very least you should be going through your skincare routine every night, says Dr. Engelman.