Applying SPF daily is a skin-care non-negotiable. It’s been drilled into us that unprotected exposure to sunlight can lead to hyperpigmentation, early wrinkles, sunburn and skin cancer. We’re definitely not our boomer mothers, slathering our skin in baby oil and frying on a beach.

Which brings us back to SPF: With such a focus on sun protection and so many products on the market, we have some burning questions about sun and skin care. How do we know which formulas are the best ones for our skin? Does SPF number matter?

We consulted esthetician Erin Burke, from Lash L’Amour in Newton, to get the real deal on SPF.

Does the SPF number matter after 50?

According to Burke, there is no scientific proof that an SPF over 50 is more effective. For daily use, you should be using at least SPF 30 to ensure some protection from the sun, but you don’t have to go any higher than 50.

“When you see sunscreens on the shelves marked as SPF 100 or 150, it’s really just a marketing ploy, it’s not any more effective,” says Burke.

Can you use sunscreen lotion for your body on your face?

If you’re concerned about skin irritation and acne, you should not be using a sunscreen body lotion on your face.

Facial SPF formulas have been tested to cause less skin irritation and are designed to feel lighter and more easily absorbed than body formulas. So, invest in a good facial sunscreen and body sunscreen!

When applying facial sunscreen, don’t forget to go all the way down the neck — an area of your body that tends to show more signs of aging because of the delicate skin there.

What is the difference between physical and chemical sunscreen?

According to Burke, physical sunscreen, also known as mineral sunscreen, sits on top of the skin and deflects UV rays from penetrating the skin. Its formula contains mineral ingredients such as zinc oxide or titanium dioxide.

In contrast, chemical sunscreen gets absorbed into the skin and causes a chemical reaction that turns the UV and UV rays into heat, releasing it from the body.

“Chemical sunscreen can also be known as synthetic sunscreen because its active ingredients are synthetic chemicals like oxybenzone and octinoxate, among others,” says Burke.

So, which formula should you choose? Well, it comes down to personal preference and skin type.

Burke says those with sensitive skin should stick to physical sunscreens which usually come in creamy formulas with moisturizing ingredients such as Vitamin E. Chemical sunscreens are lighter on the skin, but can cause irritation because, as mentioned earlier, it creates heat.

For women who have darker skin tones, physical sunscreens tend to leave behind a white sheen that sits on top of the skin, while chemical sunscreens are hardly noticeable once it gets absorbed into the skin.

Another important thing to keep in mind: Physical sunscreen is effective as soon as you put it on, but chemical sunscreens take at least 20 minutes to absorb into the skin. This means you should leave some time between putting that sunscreen on and rushing out the door!

Fact or Myth: Do you have to reapply sunscreen when exposed to water and sweat?

“Yes, water is an issue for physical sunscreen,” says Burke. After going swimming or sweating up a storm at the beach, you should reapply your physical sunscreen.

You can get away with getting wet with chemical sunscreen, it will mostly remain effective, but to stay on the safe side, re-apply any kind of sunscreen every two hours to maintain continuous protection.

Don’t want to ruin your makeup but still want to abide by the every two-hour rule? Try using facial sunscreens that you can spray on, without having to touch your face. Because who says you can’t have both brilliantly contoured makeup and sun protected skin?