Celeb dermatologist Dr. Whitney Bowe takes you to skincare school, revealing everything from how to tell what type of skin you have to why you should use a serum.

How to Tell If Your Skin is Oily, Dry or Combination

There are three types of skin: normal, combination or oily. How can you tell what type you have? All you need is a mirror!

Look at your pores in the mirror. “If you’ve got big, dilated and large pores, chances are you’ve got oily skin,” Dr. Bowe says. Likewise, if your pores are so small you can’t see them, “chances are your skin might be on the dryer side,” according to Dr. Bowe.

Meanwhile, “If you have very dilated pores in what we call the “T zone,” but everywhere else you can hardly see the pores, you probably have combination skin,” she says.

Another test you can do is the cheek pinch: “If you pinch your skin and the skin looks nice and plump, you’ve probably got normal skin.”

“But if you see lots of lines going on when you’re doing that pinch, then you probably have dry skin, or dehydrated, thirsty skin,” she says.

Should You Try the “Double-Cleansing” Trend?

It’s not as simple as soap and water, folks! Dr. Bowe recommends trying “double cleansing,” in which you first wash with an oil-based product, then follow up with a water-based product. Why? Because “like dissolves like” and your makeup products are probably oil-based. A water-based cleanser then removes all the accumulated grime from your day.

First, use the oil-based cleanser on a cotton pad to remove your makeup, then wash your face with the water-based cleanser, rinsing with warm water.

Is a Serum Really Worth It?

“I think of a serum as the workhorse of our skincare routine,” Dr. Bowe says. “It’s made of the most potent ingredients and it’s usually strongly backed by science.”

Dr. Bowe, who represents No7, recommends trying No7 Lift and Luminate Triple Action Serum, which you can buy for under $35 at Target: “It has been clinically proven to even out skin tone, causes a visible firming of the skin and their clinical studies show that 89 percent of subjects who use this serum actually had a visible reduction in the appearance of their wrinkles.”

Dr. Bowe says to follow up your serum with an eye cream and a moisturizer.

Bonus Tip: Don’t Use the Same Towel to Dry Your Hair and Face

Dr. Bowe points out that the ingredients in your hair conditioner that make your hair shiny are not so great for your face. So keep those towels separate!