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Have you ever wondered how much sunscreen you really need to protect your skin from the sun? Today, we’re going to dive into the science behind sunscreen and explore how we protect our skin from UV rays.

The magic number: 2 mg/cm²

The U.S. Food and Drug Administration (FDA) recommends applying approximately 2 milligrams of sunscreen per square centimeter (2 mg/cm²) of exposed skin to provide adequate sun protection. This guideline is based on FDA testing protocols designed to ensure that sunscreens provide their labeled SPF when used correctly (FDA, 2019).

So, without doing the math, how much sunscreen is 2 mg/cm² in real life? It’s about one ounce (30 mL), or one shot glass, for the average adult body. For the face and neck alone, 2 mg/cm² is about 1/2 teaspoon (¼ teaspoon for the face and the same amount again for the neck).

Not enough is not enough

A study published in the Journal of the American Academy of Dermatology found that most people tend to apply only 25-50% of the amount of sunscreen they need, resulting in reduced protection. Don’t be one of them! It’s also important to remember that sunscreen isn’t a one-time thing. You need to reapply every two hours or immediately after swimming, sweating, or toweling off to maintain consistent protection throughout the day.

So, what’s the deal with SPF?

You’ve probably seen sunscreens with different SPF (sun protection factor) numbers, but what do they mean? SPF measures a sunscreen’s ability to protect your skin from UVB radiation, which is the primary cause of sunburn and plays a role in the development of skin cancer. No sunscreen can block 100% of UV radiation, so additional protective measures such as staying in the shade and wearing protective clothing (hats, long-sleeved shirts and pants, sunglasses) are also important.

Broad Spectrum: Covering all the bases

When choosing a sunscreen in the U.S., look for one labeled “broad spectrum. This ensures that the product protects against both UVA and UVB rays. UVA rays can penetrate deep into the skin, causing premature aging and increasing the risk of skin cancer, and the shorter UVA rays can also contribute to sunburn. UVB rays primarily affect the surface of the skin, causing sunburn and playing a role in the development of skin cancer. Both types of radiation can be harmful, so it’s important to protect against both.

Sun protection is essential for maintaining healthy skin and preventing the harmful effects of UV radiation. So the next time you head outdoors, remember to reapply sunscreen generously and use additional forms of sun protection (hat, sunglasses, protective clothing, shade) depending on your activity and skin cancer risk factor – and enjoy the day!