SPF stands for Sun Protection Factor. This pertains mostly to UVB rays, which are the ones that result in sunburns. Rather than penetrating the deeper layers of the epidermis, UVB rays generally burn the outer, superficial layers of the skin. These rays are the ones that play a strong part in the formation of skin cancer. So, it’s important to adequately protect yourself from them. This is where SPF comes in.

Every time we go outside, we’re exposed to two different types of harmful UV rays: UVA and UVB. UVB rays are the ones that result in you getting that awful sunburn. UVA rays penetrate the deeper layers of the dermis and can cause premature aging. Long term exposure to UV radiation increases the formation of free radicals. As a result, they cause extensive damage both physically and internally.

Sunscreens are divided into two different categories: physical and chemical. A common misconception is that physical sunscreens contain natural ingredients that are better for your health. The reality is that both physical and chemical sunscreens contain chemicals. Physical sunscreens usually use titanium dioxide or zinc oxide, while chemical ones use a variety of ingredients, like aoxybenzone, avobenzone, homosalate and octinoxate.

Nothing really. Despite popular belief, physical and chemical sunscreens actually work in the same way. They form a protective film on the skin that absorbs UV light and turns it into heat. Physical and some chemical sunscreens, also reflect and scatter the incoming UV light. Both sunscreen types work effectively at protecting you from harmful UV rays.

According to the American Academy of Dermatology, you should use at least one teaspoon of sunscreen on your face. People tend to go light with their sunscreen because they either don’t like the texture or the formulation might mess up their makeup. Instead, it’s best to take a “more is more” approach and apply more than you think you need. As for the body, the AAD suggests “one ounce, enough to fill a shot glass,” to protect you from UV rays. Remember to reapply throughout the day for long-lasting protection.

Most sunscreens contains silicones that form an occlusive, protective layer on the skin. To get the most from your SPF, you’ll want to apply it after your moisturizer. This is to avoid disturbing your SPF or decreasing its protection in any way. But, you can also use a moisturizer and SPF combination, which takes care of that in one simple step.

Nope. While it can be a hassle to find sunscreen formulas that work with acne-prone skin, rather than skipping sunscreen altogether, which would actually cause more damage, Sadick suggests “choosing a formulation that is light, water-based, and avoids any products that contain heavy oils like coconut, beeswax, and cinnamon oil.”

Most sunscreens will suggest applying 10 to 15 minutes before heading out the door. This idea perpetuates the myth that you have to apply your sunscreen earlier so it has time to “activate.” But, this has less to do with activation and more about creating an even layer of sunscreen on the skin.

Your sunscreen doesn’t actually have to activate—it works from the very moment that you apply it. But, in order for an SPF to do its job, you want to allow it to create an even film on the skin. The more even your application, the more complete protection from UVA and UVB rays.

SPF stands for Sun Protection Factor. This pertains mostly to UVB rays, which are the ones that result in sunburns. Rather than penetrating the deeper layers of the epidermis, UVB rays generally burn the outer, superficial layers of the skin. These rays are the ones that play a strong part in the formation of skin cancer. So, it’s important to adequately protect yourself from them. This is where SPF comes in.

Every time we go outside, we’re exposed to two different types of harmful UV rays: UVA and UVB. UVB rays are the ones that result in you getting that awful sunburn. UVA rays penetrate the deeper layers of the dermis and can cause premature aging. Long term exposure to UV radiation increases the formation of free radicals. As a result, they cause extensive damage both physically and internally.

Sunscreens are divided into two different categories: physical and chemical. A common misconception is that physical sunscreens contain natural ingredients that are better for your health. The reality is that both physical and chemical sunscreens contain chemicals. Physical sunscreens usually use titanium dioxide or zinc oxide, while chemical ones use a variety of ingredients, like aoxybenzone, avobenzone, homosalate and octinoxate.

Nothing really. Despite popular belief, physical and chemical sunscreens actually work in the same way. They form a protective film on the skin that absorbs UV light and turns it into heat. Physical and some chemical sunscreens, also reflect and scatter the incoming UV light. Both sunscreen types work effectively at protecting you from harmful UV rays.

According to the American Academy of Dermatology, you should use at least one teaspoon of sunscreen on your face. People tend to go light with their sunscreen because they either don’t like the texture or the formulation might mess up their makeup. Instead, it’s best to take a “more is more” approach and apply more than you think you need. As for the body, the AAD suggests “one ounce, enough to fill a shot glass,” to protect you from UV rays. Remember to reapply throughout the day for long-lasting protection.

Most sunscreens contains silicones that form an occlusive, protective layer on the skin. To get the most from your SPF, you’ll want to apply it after your moisturizer. This is to avoid disturbing your SPF or decreasing its protection in any way. But, you can also use a moisturizer and SPF combination, which takes care of that in one simple step.

Nope. While it can be a hassle to find sunscreen formulas that work with acne-prone skin, rather than skipping sunscreen altogether, which would actually cause more damage, Sadick suggests “choosing a formulation that is light, water-based, and avoids any products that contain heavy oils like coconut, beeswax, and cinnamon oil.”

Most sunscreens will suggest applying 10 to 15 minutes before heading out the door. This idea perpetuates the myth that you have to apply your sunscreen earlier so it has time to “activate.” But, this has less to do with activation and more about creating an even layer of sunscreen on the skin.

Your sunscreen doesn’t actually have to activate—it works from the very moment that you apply it. But, in order for an SPF to do its job, you want to allow it to create an even film on the skin. The more even your application, the more complete protection from UVA and UVB rays.