Last week, I talked about the best moisturizers for combination skin, but that brought me to another more simple—but essential—skincare question from a reader: how to know what type of skin you have. Although it's impossible to categorize something as nuanced as your skin into a singular class, it does serve as a good baseline when looking for skincare products.

"Skin type is primarily determined by genetics," says Hadley King, MD, a board-certified dermatologist in New York City. "That being said, it can also be influenced by medications, particularly hormonal and cholesterol-lowering medications. Topical products should also be taken into account—for example, if you used topical retinoids regularly, this may make your skin more sensitive."

And yes, skin type can change with age. As we get older, our skin gets drier since it goes through significant hormonal shifts. It's also possible to develop sensitivity over time, so don't assume that your skin type today will be the same skin type 10 years from now. It's important to consistently pay attention to your skin in order to understand where it's at and how it evolves.

Now, for the nitty gritty—here's a basic breakdown of each skin type.

Dry Skin

Dry skin is characterized by ashy, dull, and sometimes flaky skin, says Dr. King. Your pores often feel tight (especially post-cleansing). Your skin will become naturally drier as you age since your skin's natural oil production starts to decrease. If your complexion is chronically dry, it means that you have a compromised skin barrier that water easily evaporates from. The skin must be regularly supplied with thick moisturizers (including humectants, emollients, and occlusives) to feel satisfied. 

However, it's important to note that dryness and dehydration aren't quite the same thing. To put things simply, dryness refers to a skin type, and dehydration refers to a skin condition. Dry skin is a result of a lack of oil in the skin, while dehydrated skin is the result of a lack of water in the skin. People with dehydrated skin don't necessarily have dry skin—it could be oily, combination, or normal skin that is simply lacking hydration.

Oily Skin

People with oily skin have overactive oil glands that produce more sebum than the average face. As a result, you'll notice that your skin is particularly shiny even after an hour or two of washing. Oily skin is also commonly acne-prone, although it doesn't have to be. However, Dr. King notes that because sebum can lead to clogged pores, acne is a common occurrence.

Combination Skin

Combination skin is a tricky beast to tame. You tend to get oily in the T-zone area and dry on other areas of the face, meaning you can be prone to pimples and dry patches at the same time. Unfortunately, derms say combination skin is the most common of all skin types. The good news? It's possible to maintain. Case in point: There are hybrid moisturizers that work for all-over application without triggering one portion of your face or the other.

Normal Skin 

Normal skin is neither particularly oily nor particularly dry overall. "While people with dry or oily skin types find that certain ingredients are too irritating, you may find that almost everything works for you," says Dr. King. This is definitely the easiest skin type to have, so consider yourself lucky—and give your parents some love for passing down some pretty awesome genes.

Sensitive Skin

Sensitive skin can be identified by how it reacts to topical products. You might experience burning or itching sensations when using certain products, especially peels (i.e., retinol) or ones with fragrance. Sensitive skin is also prone to skin conditions like eczema, dermatitis, psoriasis, or rosacea, so if you have any of those, chances are you have sensitive skin. Remember that your skin can get become sensitive through things like aging and excessive retinol use.

Now to get to the one question we all need the answer to: What is your skin type? If you want an easy technique to determine your skin type, there is a quick test you can do at home with blotting paper.

Apply two clean blotting sheets on different parts of your face: one on your forehead, and one on your cheeks. Afterwards, hold the sheets up to light to see how much oil was absorbed. The more oil there is on the paper, the more likely you have oily skin. If there is little to no oil visible on either sheet, you have drier skin. And if the blotting sheets reveal drastically different levels of oil, your skin is probably combination.

Keep in mind that you can have more than one skin type. In fact, it's likely. For example, someone with sensitive skin can be dry or oily. This is when things get a bit more complicated, so I've included a more comprehensive test below. If you find that two or more points in any one of the categories describe you, then go for the products labeled for that skin type(s). From there, you can build a personalized routine with products that work best.

Choose Products for Oily Skin If:

• By midafternoon, a greasy film has developed on your face, even though your skin felt fine when you left home this morning.

  The culprit? You probably have an oily T-zone.

• Acne breakouts are making you feel like your 16-year-old self.

  (Minus the homework and boy-band crushes.)

• The more you scrub your skin, the oilier it seems to get, and the more you seem to break out.

  That's because stripping the skin of oils prompts it to produce even more oil to compensate and restore balance.

Choose Products for Dry Skin If:

• Patches of skin on your face or body are flaky, whatever the season.

  Or if you find that "winter skin" never seems to disappear.

• Your complexion appears dull and lackluster, no matter how many "brightening" products you apply.

  The reason? Dry skin doesn't reflect light as well as hydrated skin.

• Moisturizer doesn't really make a difference, no matter how thick and creamy it is or how much you apply.

  This happens when the moisturizer can't penetrate the scaly skin barrier.

Choose Products for Sensitive Skin If:

• Regular beauty products, especially ones that are scented, leave your skin irritated, red, and sometimes stinging.

  (Ugh.)

• Changing the kind of laundry detergent you use sets off a rash on your finicky skin.

  Even using a new towel can make you see red.

• Some spa treatments, such as intensive facials and alpha hydroxy peels, feel too strong.

  You would much prefer a massage to having someone pick and poke at your face.

Choose Products for Combination Skin If:

• Your forehead is typically shiny, while appearing dry or normal on the cheeks.

  Oil patrol for your T-zone is necessary.

• You tend to break out in the same areas.

  Most likely, it will be the aforementioned oily parts.

• Different skincare products work in some areas, but irritate others.

  You might be tempted to mix and match products instead of using an all-in-one moisturizer.

Choose Products for Normal Skin If:

• Forgetting to bring a cleanser on a trip is no problem since you can just use the one at the hotel.

  Did I mention how lucky you are?

• In your makeup routine, setting sprays and mattifying powders don't really seem necessary.

  Seriously, you're so lucky.

• You're able to tolerate higher levels of typically irritating ingredients, such as retinol or glycolic acid.

  Go thank your parents right now.

The post Ask a Beauty Editor: How to Know Your Skin Type appeared first on Real Simple