Sun and sunscreen 101 – everything you need to know about sun protection with recommendations

I’ve listed our favorites in a separate article (update coming soon to my instagram!), but first some sunscreen and sun protection basics (okay, this is a little beyond the basics. I couldn't help myself!). I've also listed recommendations based off of skin type/concern at the bottom of this article!

sun and sunscreen 101 - everything you need to know about sun protection with recommendations

Summary:

  • Sun exposure is linked to the development of malignant melanoma, squamous cell carcinoma, basal cell carcinoma and the development of fine lines and wrinkles.
  • There are two mechanisms of sunscreen. Physical sunscreens form a barrier to prevent sunlight absorption by the skin. Chemical sunscreens absorb sunlight and dissipate the energy as heat.
  • Children younger than 2 years of age should only use physical sunscreens. Children younger than 6 months should avoid sun exposure.
  • The American Academy of Dermatology currently recommends daily application of SPF 30+ with broad-spectrum protection, but SPF 50 with broad spectrum protection is a safe choice since most people don’t apply enough sunscreen (and some sunscreens may not live up to their reported SPF)!
  • Sunscreen is only part of the sun protection picture! Avoidance of the sun by seeking shade and/or not going outside between 10 am – 2 pm and wearing wide brimmed hats, long sleeves, and sunglasses are additional forms of sun protection that ideally should be used with daily sunscreen use.

Now let’s learn.



What’s so bad about sunshine?

The sun emits light rays in the wavelengths 270 - 400 nm. Shorter wavelengths (ultraviolet light C) are filtered out by the ozone layer. Ultraviolet light A (UVA) and ultraviolet light B penetrate the skin.

Classically, UVB rays are considered burning rays and UVA rays are considered aging rays, but they both contribute to all 5 mechanisms of adverse UV effects to varying degrees. UVA is divided into UVA1 and UVA2 rays, with UVA2 rays acting similar to UVB.

Short-term effects of sun exposure include burning, skin pigmentation, delayed tanning, epidermal hyperplasia, free radical formation, vitamin D synthesis, and photosensitization. Short-term effects are mostly secondary to UVB and UVA2 rays.

Long-term effects of sun exposure include photoaging (fine lines and wrinkles), photoimmunosupression, and photocarcinogenesis (malignant melanoma, squamous cell carcinoma, basal cell carcinoma).


What does sunscreen do?

Sunscreen protects your skin from the harmful effects of UVA and UVB radiation (see previous question for harmful effects).

Sunscreen is only one form of photoprotection. Other important ways to protect yourself from sun damage include –

  1. Avoid it! Seek shade and/or do not go outside between 10 am – 2 pm.
  2. Throw yourself shade. Wear wide brimmed hats, long sleeves, and sunglasses when in the sun.

Of note, car wind shields provide UVA+UVB protection, but car windows standardly only provide UVB filtration. For that reason, it is also best practice to avoid driving between the hours of 10 am – 2 pm and treat long daytime car drives as high sun exposure activities. Post-market window tinting adds UVA protection to windows.


What type of sunscreen do I need?

In short, you want SPF 30+ with broad-spectrum protection. Add water resistance for beach, pool, lake, sprinkler days. We’ll discuss the types of sunscreen and types of skin to better understand these recommendations.


What’s good coverage?

The American Academy of Dermatology recommends using at least SPF 30 with broad-spectrum activity everyday. Sunscreens filter out a different spectrum of UVA and UVB light depending on the active ingredient in the specific sunscreen.

Traditionally, sunscreens were only marketed on their sun protection factor (SPF). Sun protection factor (SPF) is an estimated magnification of minimum erythema dose (MED) - the minimum amount of light exposure that produces visible reddening of the skin. Skin that normally burns in the sun after 20 minutes should tolerate the same sun exposure 30 times longer when SPF 30 if adequately applied and reapplied (600 minutes vs 20 minutes).

We learned earlier that not all UV rays cause sunburn (see question 1 for a review). SPF is essentially a marker of the sunscreen’s UVA2 and UVB filtering capabilities. Adequate SPF without UVA1 protection will protect you from the acute burning/tanning of sun exposure, but will not protect you from the long-term photoaging and carcinogenic effects of sun exposure. “Broad spectrum” signifies that the sunscreen provides significant UVA coverage in addition to the UVB coverage marked by its SPF.

Sunscreen labeling is regulated by the FDA. The chart below lists regulations.

Sunscreen labeling regulations

You are correct in thinking that not everyone actually needs SPF 30 to prevent burning, but everyone needs some sunscreen and there’s really no big price or cosmetic difference for SPF 30 vs lower, so I recommend sticking to that recommendation. For your knowledge, the Fitzpatrick scale was developed by Thomas B. Fitzpatrick in 1975 and categorizes individuals based off of their response to UV light. Your skin type dictates the SPF you need to prevent burning. Fitzpatrick skin phototype I is at highest risk for sun damage.

  1. Fitzpatrick skin phototype I: always burns, never tans
  2. Fitzpatrick skin phototype II: burns easily, tans with difficulty
  3. Fitzpatrick skin phototype III: mild burns, tans gradually
  4. Fitzpatrick skin phototype IV: rarely burns, tans easily
  5. Fitzpatrick skin phototype V: Very rarely burns, tans very easily
  6. Fitzpatrick skin phototype VI: never burns, tans very easily

Of note, the Fitzpatrick scale correlates with skin tone, but they are not the same. Darker individuals do not burn easily due to natural sun protection (approx. SPF 10) and have decreased risks of skin cancer formation and photoaging but these risks are not zero. Also, my face is an entire phototype less than the rest of the my body because my daily retinoid use increases sun sensitization.


What’s a physical sunscreen?

Basically, sleeves in a bottle.

Physical sunscreens are made of inorganic particles (titanium dioxide and zinc oxide most commonly) that form a barrier on top the skin. This barrier deflects and scatters UV rays preventing absorption by the skin. The particles of this barrier are traditionally very large and produce a chalky sheen along the skin. There has been recent innovation in this area with newer, smaller particles that allow for a more translucent finish. These micronized particles, however, act as both physical and chemical sunscreens.

In general, physical sunscreens are not as effective as chemical sunscreens. A 2016 consumer report found that 43% of the 69 sunscreen tested did not live up to their reported SPF. The highest percentage of the “false” SPFs were physical sunscreens. The micronized particles, although trendy, appear to be the least effective sun filter.

Children less than two years of age and people with an allergy to active ingredients of chemical sunscreens should use 100% physical sunscreens. For most people, I recommend chemical sunscreen or a physical+chemical combination.


What’s a chemical sunscreen?

Basically, your skin’s secret service; it takes the hit to protect you.

Chemical sunscreens absorb UV radiation and dissipate the energy as heat. Chemical sunscreens include para-aminobenzoic acid [PABA], octyl methoxycinnamate, octisalate, homosalate, trolamine salicylate, oxybenzone*, octocrylene, ensulizole, avobenzone**, mentyl anthranilate, etc

*Oxybenzone, padimate O, and avobenzone are the three most common causes of allergic and irritant contact dermatitis with sunscreen application.

**avobenzone combined with a stabilizer, such as octocrylene, is suggested as the sunscreen filter with the widest UVA+UVB protection.


How much sunscreen?

More than you're probably applying! People commonly under apply sunscreen. Current recommendations to achieve the advertised SPF in an adult is to apply

  • 1 teaspoon of sunscreen to the face/head/neck
  • 1 teaspoon to each arm
  • 2 teaspoons total to the front and back torso
  • 2 teaspoons to each lower extremity

Two tricks to make sure you obtain desired protection:

  1. Apply sunscreen twice for each application. This will decrease skip areas.
  2. Use twice the desired SPF.

How often?

It is recommended that sunscreen be applied 15 minutes before sun exposure and reapplied every 2 hours during high sun exposure. For normal, daily use, one to two applications is probably sufficient. A May 2016 JAAD study found that the protective effects of facial moisturizer with SPF 15 broad-spectrum protection are maintained for at least 8 hours. Sunscreen should always be reapplied immediately after water exposure.


What about kids?

Use only physical sunscreens in children less than two years of age. Try to avoid the sun as much as possible in infants less than six months of age. If the infant has to have sun exposure, use diligent non-sunscreen sun protective methods and discuss sunscreen choice with your pediatrician. There is concern for higher absorption rates and lower excretion rates in infants putting them at higher risk for toxic effects of sunscreen absorption; to my knowledge, this concern is only theoretical.


What about spray sunscreens?

There has been some concern about spray sunscreens.

In some, the spray mist is so light that it can be picked up by the wind and never land on the skin! My personal favorite spray sunscreen is cerave. It goes on thicker than others, so it’s easy to see the sunscreen hit the skin.


What about reports that sunscreen ingredients cause cancer?

Sunscreens are considered over the counter drugs in the US. Maximum concentration of active ingredients, labeling, and truthfulness of sun SPF are all under regulation by the Food and Drug Administration (FDA). Because of strict regulation, the US has the lowest variety of sunscreen active ingredients available.

There have been reported concerns for the estrogenic and anti-androgenic effects of oxybenzone. An animal model showed increased uterine weight in rats fed oxybenzone, but Wang et al. estimate it would take approximately 277 years of daily sunscreen application of 6% oxybenzone to achieve those levels in humans (so, completely irrelevant results). A human study in Switzerland did show an association between, high oxybenzone levels in mothers’ urine and decreased birth weight in girls/increased birth weight and head circumference in boys. The mode of oxybenzone intake was not documented in the study, and no firm conclusions can yet be made from this data. Remember, associations do not necessarily mean there’s a cause and effect relationship. More studies are underway to better understand the connection.

For more on this, I recommend one of my favorite articles by NYU dermatology resident Joyce Parks of Tea with MD: Myths about sunscreen safety


What about vitamin D?

Biologically active vitamin D - Vitamin D3 (cholecalciferol) - is either ingested from the diet or synthesized in the skin from 7-dehydroxycholesterol. It then undergoes further modification in the liver and kidney.

Since sunscreen blocks the skin’s absorption of UV light, it also blocks the conversion of 7- dehydroxycholesterol to vitamin D3 by UVB radiation. Studies have shown that regular sunscreen users do have reduced vitamin D levels, but the levels are usually still within normal levels (maybe because they’re not applying enough sunscreen). Vitamin D supplementation is easy enough, however. My vitamins are kind of my favorite part of my day, so tasty!


What about vitamin C, vitamin E, green tea?

It is unclear if these vitamins provide sun protection, but antioxidants are commonly included in facial sunscreens with the claim to reduce reactive oxygen species released by UV exposure.


now what you came here for - recommendations!

below I've listed recommendations based off of skin type/concern, my personal favorites are here!


Fitzpatrick skin types I-III

unless allergic, use sunscreens with active chemical UV filters. Your skin type is at the highest risk of sunburn, skin cancer, and photoaging. Chemical sunscreens, in general, are more effective UV filters than physical sunscreens ( avobenzone and octocrylene TOGETHER is maybe the most effective UV filter). There’s limited data, but antioxidants may be of benefit. Photoprotection is a must for you.


Fitzpatrick skin types IV-V

Unless allergic to chemical sunscreens, avoid physical sunscreens. This is basically the same advice for Fitzpatrick skin types I-III but for a different reason. The most effective physical sunscreens have large particles which will leave a white sheen on your face. A pure physical sunscreen that doesn’t leave a white sheen may not be doing its job as well as it claims.


Sensitive skin

Use physical sunscreens. Consider using SPF 50+ and double applying before exposure. Consider adding antioxidants to your sun protection routine, despite the lack of conclusive data.


Those with skin conditions

If UV light worsens your skin condition, photoprotection is a must – specifically sun avoidance. Chemical sunscreens would be ideal, but may also irritate your skin. If so, use a physical sunscreen and follow the recommendations for sensitive skin.


kids

Younger than 2 years of age: physical sunscreen only. Considering using SPF 50 and double applying

before exposure.

Less than 6 months: avoid the sun. Use photoprotection and a sunscreen recommended by your pediatrician

for rare sun exposures.


I hope that answered all the questions you didn't know you had! Be sure to check out my personal favorite sunscreens here!

leave additional questions/comments/concerns below.

What other topics do you want me to tackle?

elyse love, md


Sources:

  1. Bolognia, J., Jorizzo, J. L., & Schaffer, J. V. (2012). Dermatology. Philadelphia: Elsevier Saunders.
  2. Duration of efficacy for daily facial sunscreen product Journal of the American Academy of Dermatology , Volume 74, Issue 5 , AB225
  3. Jansen R, Osterwalder U, Wang SQ, Burnett M, Lim HW. Photoprotection: part II. Sunscreen: development, efficacy, and controversies. J Am Acad Dermatol. 2013 Dec;69(6):867.e1-14; quiz 881-2. doi: 10.1016/j.jaad.2013.08.022. PubMed PMID: 24238180.
  4. Get the Best Sun Protection. (2016, May 17). Retrieved from http://www.consumerreports.org/sunscreens/get-the-best-sun-protection/
  5. Swetter, S. (2016, June 2). 5 Questions: Susan Swetter on choosing a sunscreen. Retrieved from https://med.stanford.edu/news/all-news/2016/06/5-questions-susan-swetter-on-choosing-a-sunscreen.html
  6. Wang SQ, Burnett ME, Lim HW. Safety of oxybenzone: putting numbers into perspective. Arch Dermatol 2011;147:865-6.