Sunscreen 101: UVA vs. UVB, What SPF Means, Sunscreen & Makeup

Sunscreen

Disclaimer: I am not a doctor, licensed esthetician, skincare expert, etc. This is information I have gathered from reading many different sunscreen-related articles throughout the past few years. I’ve provided links for reference purposes. As always, please consult your doctor and/or dermatologist for the latest and most accurate, up-to-date information.

Why sunscreen?

Wearing sunscreen will help prevent your skin from burning from harsh UVB rays and reduce the effects of UVA rays on the deeper layers of your skin–it may help reduce the signs of aging later on down the road as well as lower your exposure risk to skin cancer.

What are UVA and UVB?

  • UVA rays are the kind that have the greatest effect on you… that you don’t necessarily see right away. This includes aging and wrinkles as well as increase the risks of skin cancer.  Think of UVA as the AGING (and cancer-causing) rays.
  • UVB rays are the kind that you’ll notice right off the bat,  because UVB rays are generally responsible for sunburns.  Think of UVB as the BURNING (sunburn-causing) rays.

This is a very short and sweet summary to get the main points out, but you can check out this article for a more in-depth explanation.

Is higher SPF better?

Not, not necessarily. First, remember that “SPF” is only a rating on effectiveness of UVB rays, not UVA.   SPF 15 blocks roughly 93% of all UVB, while SPF 30 blocks 97%, and SPF 50 blocks 98%. (See SkinCancer.org.) If you are out and about, many organizations recommend reapplying sunscreen every two hours (especially if you’re spending the day in the sun). It is also more important to look for a broad spectrum sunscreen than one merely with a high SPF rating.

The way SPF works is if it takes you 10 minutes to start burning normally, wearing SPF 15 would mean it would take 15 times as long to burn–150 minutes.

How much SPF do I need? Do I need to reapply my sunscreen throughout the day?

Most recommendations seem to indicate a a full shotglass’ amount for your entire body applied thirty minutes before sun exposure and reapplied every two hours. If you’re in the water or sweating, it is even more important to reapply regularly. Even water-resistant sunscreens (designed for 40 minutes of protection in the water) and waterproof sunscreens (designed for 80 minutes of protection in the water) need to be reapplied after a romp in the water. (See AAD.org.)

How do I reapply sunscreen over makeup?

According to WebMD, it is much better to choose a moisturizer or lotion/cream based SPF product rather than a foundation or powder with SPF in it–you may not get enough coverage if it’s within a foundation (particularly a powder) or cosmetic product.   Bauman (an expert in the aforementioned article), recommends reapplying sunscreen once during the day for day-to-day wear. To reapply sunscreen over an already-done face, consider a sunscreen spray (but made for the face, not the body), patting a layer of sunscreen or SPF-based tinted moisturizer onto the face (don’t rub), and/or pressed powder (with a sponge for better adhesion) with SPF.

In general, the ingredients in sunscreen degrade when in direct UV contact, so if you’re sitting in an office building all day, it may not be necessary to reapply.  Always remember to apply sunscreen liberally–don’t hold back–and be thorough about it.  If cost is a worry, look for a more affordable sunscreen rather than a $300/jar sunscreen!

What ingredients should I look for?

Any sunscreen or sunblock should list what ingredient(s) it uses to accomplish sun protection. The rule of thumb is to look for a sunscreen with “broad-spectrum” protection. This means that it uses ingredients that cover the majority of the UV spectrum (so both UVA and UVB protection).

  • UVB (290-320nm): Aminobenzoic Acid (PABA), Cinoxate, Dioxybenzone, Ensulizole, Homosalate, Octocrylene, Octinoxate, Octisalate (Octyl Salicylate), Oxybenzone, Padimate O, Sulisobenzone, Trolamine Salicylate, Titanium Dioxide, Zinc Oxide
  • UVA (320-340nm): Dioxybenzone, Ecamsule (Mexoryl), Helioplex, Meradimate, Oxybenzone, Sulisobenzone, Titanium Dioxide, Zinc Oxide
  • UVA (340-400nm): Avobenzone, Zinc Oxide

Physical blockers like Titanium Dioxide and Zinc Oxide may give some deeper skin tones a white cast (as they are, literally, physically blocking the rays). Some may be allergic or sensitive to chemical sunscreens and may need to opt for physical blockers instead. Physical blockers protect skin by deflecting or blocking harsh UV rays, while chemical blockers/sunscreens usually absorb them. (Most other sunscreen ingredients beyond titanium dioxide and zinc oxide are chemical sunscreens, for reference.) Physical blockers tend to be more stable, while chemical sunscreens may degrade and are often paired with other sunscreen ingredients to increase stability. (See more information at AMF.org.)