Octocrylene. Octo (like the lady with 8 kids) – cry- lean.
Sunscreens have been around forever, mostly in the form of plants and dirt people rubbed onto their skin. Not terribly effective, sadly. Ancient Egyptians used aloe vera, extracts of rice, and pounded out calcite and clay to protect their skin. In the Philippines borak was used – made from water weeds, rice and spices. Zinc oxide has been around for thousands of years.
The first synthetic sunscreens were created in the 1920s, and were made commercially available by L’Oreal in 1936.
Sunscreen became more popular after WWII, when we sent a bunch of pale skinned soldiers to the Pacific Islands. Ouch.
These original sunscreens are estimated to have had an SPF of about 2. Also not terribly effective.
Why do we use sunscreen?
We use sunscreens to prevent sunburn, skin cancer, wrinkles, and hyperpigmentation.
The incidence of melanoma has increased in the 15-39 year age range by 3% per year since the 90’s. It is the 2nd most common cancer for women in their twenties, 3rd for men. Dr Sophie J. Balk (Former Chairperson, AAP Committee on Environmental Health) writes that this was caused by the thinning ozone layer, the fact that people are wearing less clothing, intentional tanning, and tanning beds.
Skin cancers like squamous cell carcinoma, melanoma, and possibly basal cell carcinoma can be prevented by using sunscreen – if you use the right one in the right way.
Who should use sunscreen?
It is especially important for children and people with fair skin, fair eyes, freckles, sun sensitivity, moles, or a family history of melanoma.
But really, everybody.
The Science: What Does the Damage?
Sunlight has wavelengths between 290-3200 nm; the light that we see, or “visible light” runs between 380 to 740 nanometers. Wavelengths in the top, violet part of the rainbow are 380-450 nm, so the wavelengths shorter than violet are called “Ultraviolet.” UVB rays are the 290-320 range (about 5% of the total); UVA rays are 320-400 (95% of the total).
UVB rays burn, leaving you with redness and pain, and these were traditionally the rays we tried to block. UVB does contribute to skin cancer but since it does not penetrate as deeply as UVA it seems to not be the cause of the most deadly of skin cancers, the melanomas.
UVA light does not cause reddening or pain, and most conventional sunscreens do not block it. It does however penetrate deeply into the skin to cause the damage to DNA in cells (melanocytes) that can lead to melanoma.
UVB is more intense midday (from 10AM – 2PM), in the summer, closer to equator, and at high altitude. UVA light is constant through the day and year.
Window glass absorbs UVB, not UVA.
Both reflect off water, sand, snow, and concrete to increase exposure.
UVB and UVA penetrate water to a depth of about 60 cm (about 3 feet).
How to protect yourself from these evil rays?
Best, of course, is to avoid them. Stay out of the sun, especially between 10AM and 4PM.
Cover up. Light weight, long sleeved shirts and long pants are protective while they are dry. There is a UPF rating for fabrics, from UPF 15-50. Above 30 is considered sun protective, and more is better. There are swim shirts for kids that are protective even when wet.
Wear a hat with a brim.
Wear sunglasses with 99% UR protection.
Use sunscreen. Sunscreens absorb or reflect the sun’s ultraviolet rays, depending on the ingredients.
- Sunscreens come in lotions, gels, or sprays.
- They generally last about 3 years on the shelf.
- SPF should be 30 or higher.
- The words “broad spectrum” should be on the label, since only these have UVA protection that is proportional to the UVB protection.
- The only chemical sunscreens available in the US that protect from UVA are avobenzone (which can be irritating and allergy producing) and Mexoryl SX and XL, available only from L’Oreal (they have a patent). Outside of the US, Tinosorb S & M and Uvinul A Plus block UVA. Mineral sunscreens also block UVA.
- Look for “water resistance” on the label as well, especially if you will be swimming or sweating.
- Apply sunscreen 20 min before exposure so that it has time to form a thin, even, protective film.
- Apply 2 mg/cm2: this is about 2 tbsp for the average adult (about a shot glass, per the Dermatology Association), and about 1/4 tsp for the face. If you put on less, you get proportionately less protection.
- Reapply sunscreen every 2 hrs or if you sweat, swim, or rub it off; stronger sun screens do not last longer and while newer sunscreens are very photostable, they do still rub off.
Sunscreens come in two basic forms, and combinations of the two forms.
Mineral (physical, inorganic) sunscreens include zinc oxide and titanium dioxide. They are usually better for sensitive skin, but they can leave a white cast and tend to be thick. They work more by reflecting sunlight, although they do absorb some. They do block UVA as well as UVB – zinc oxide more effectively than titanium dioxide.
The second type is Chemical or Organic sunscreens. They apply more like moisturizer and don’t leave a white cast. They work by absorbing sunlight’s high energy rays, although they do scatter and reflect some in the same way as mineral sunscreens.
Common Chemical/Organic sunscreens in the US:
- P-Aminobenzoic acid
- Padimate O
- p-Aminobenzoic acid
- Menthyl anthranilate
- Octyl methoxycinnamate
- Trolamine salicylate
- Octyl salicylate
- Mexoryl SX & XL
Common questions about sunscreen:
For much of this information I have to thank LabMuffin, because I am no chemist. She is a PhD chemist who educates on the chemistry behind skin and beauty products. She is amazing, and I highly recommend checking her out!
Don’t kids need sunshine to make vitamin D?
Yes, but they only need 5-30 minutes in the sunshine about twice a week, depending on their skin tone. Also, vitamin D is in milk and comes in pill form.
Should we worry about nanoparticles from mineral sunscreens?
The nanoparticles made from grinding up the mineral sunscreens (so they don’t look white on the skin) are too big to penetrate the stratum corneum and get to live skin cells.
What ingredients are the most irritating or allergic?
- Padimate O
Which ingredients are the least likely to break down in sunlight?
- Tinosorb S and Tinosorb M (not in the US yet, hopefully soon!)
- L’Oreal’s Mexoryl SX and Mexoryl XL
- Mineral sunscreens
But don’t sunscreens have hormonal effects?
Yes, some of the chemical/organic ones do, but very little. One of the worst is oxybenzone, and to have a hormonal effect we would have to use it continuously for 277 years. Enzocamine, Padimate O, octinoxate, and homosalate also have hormonal effects in minuscule amounts.
Don’t some medicines make people react more to sunlight?
Yes. A short list of meds on which you should avoid sunlight:
- NSAIDS (ibuprofen, naproxen)
- tretinoin (retinols)
Aren’t there plants that make people burn more easily?
Yes. Plants that produce furocoumarins, like limes, can cause a burn and hyperpigmentation when exposed to sunlight.
Can I use a sunscreen/insect repellent combination product?
The AAD recommends purchasing and using these products separately — sunscreen needs to be applied generously and often, whereas insect repellant should be used sparingly and much less frequently.
Are sprays safe and effective?
Current FDA sunscreen regulations do not apply to sprays, so I don’t know. They should not be used near heat or open flame (no smoking!), and should not be inhaled.
What will the UV index for tomorrow be? Check out www.weather.com.
What those labels mean:
SPF stands for “Sun Protection Factor,” and measures sunburn producing UVB rays. The number is how much burning radiation penetrates through the sunscreen. An SPF of 20 means that 1/20th of the rays reach the skin. Above an SPF of 50 you don’t see any real difference.
SPF Equivalence requires UVA protection of at least 1/3 the SPF for UVB. This labeling is seen more in Europe.
PPD is “Persistant Pigment Darkening.”
Star ratings are used in UK and Ireland, between 1 and 5 stars.
PA is “Protection Grade of UVA”, used in Asia, between PA+ to PA++++.
If “Water resistance” is on the label, it should say whether it is resistant to swimming or sweating and for how long.
If you can, please share this blog. The sun is shining outside and sunscreens can be very confusing!