Fact: Just one blistering sunburn before age 18 doubles your chances of developing melanoma later in life.

What it does: Skin is the largest organ of your body and therefore performs many functions that are often taken for granted. For example, shivering when you’re cold is a response given by the brain to the skin telling it to keep heat in. Conversely, when you’re hot, the skin sweats as a way to reduce your body temperature. Skin is also a waterproof barrier against ultra-violet radiation (UVR) and infectious microorganisms.

It’s biggest threat: Skin cancer. When sunrays (UVR) strike the skin, it scatters, is reflected, or is absorbed. The UVR that is absorbed is made up of UVB (the burning rays) and UVA (the aging rays), and both harm the cell’s DNA and compromise the immune system. This damage, in turn, weakens your natural defense to cancer.

Why you’re at risk: A 2014 report by the Canadian Cancer Society found that melanoma is one of the fastest rising of all cancers. People who are most at risk are those with fair skin that burns or freckles, rather than tans; and those who spend a lot of time in the sun, use indoor tanning, or live (or have lived) in a hot climate such as Florida, the Caribbean, or northern Australia. Equally important to know, anyone can get skin cancer, even people who have darker skin.

Keep it healthy: Wear a broad-spectrum sunscreen with a minimum SPF of 30 on your face, neck, and on exposed arms and legs all year round. Keep in mind that 70 percent of UV rays can penetrate through clouds, so even on overcast days it’s wise to wear sunblock. And if you’re planning on hitting the slopes this winter, be sure to cover your epidermis, as sunlight reflects off the snow so you can get a double dose of sun rays.