Sunscreen
Do we expect too much from our sunscreen?
Just because a product is labled SPF 30, does that mean you can stay out 30 times longer without burning?
Probably not
Let's explore the issues involved.
Sunscreen Composition
Active ingredients that protect the skin from ultraviolet radiation (UV) fall into two main categories: chemical and mineral.
CHEMICAL
Don’t be misled by the term “organic sunscreen.” It’s not comparable to organic spinach, and does not indicate that the product is natural or mineral-based. Instead, it refers to the sunscreen having active ingredients based on organic chemistry. To develop a sunscreen, chemists at the manufacturer combine FDA-approved organic chemicals that yield a product which will effectively absorb the sun’s most damaging wavelengths of UV radiation.
MINERAL
Many people are attracted to the natural quality of the zinc and titanium that are FDA-approved in the manufacture of mineral sunscreens . The thick zinc oxide paste that surfers smeared on their nose in the 1960s is highly effective but no one wants to use something like that on their entire face, much less on larger areas.
To make zinc and titanium cosmetically acceptable they must be pulverized into nanoparticles. We don’t see those ultra tiny particles but now they mostly absorb light rather than reflecting it (similar to how the active ingredients in a chemical sunscreen work). Some people are wary of exposure to nanoparticles. Studies have shown that those in sunscreen are not absorbed through intact skin so the FDA has not issued any safety concerns about the zinc and titanium in sunscreens. However, they should not be applied to an open wound or rash, and should not be ingested or inhaled (which is why they are not recommended in a spray formulation).
Broad Spectrum
The sun’s UV radiation spans a wide range of wavelengths (a broad spectrum) sub-classified as UVA and UVB. In general, UVB are the burning rays and UVA are the aging rays. Both are carcinogenic. A good sunscreen should absorb as much of each as possible. The FDA has acknowledged this by creating a test that manufacturers can perform. If a sunscreen product passes the test, it can be labeled “Broad Spectrum.” Be sure to look for the Broad Spectrum designation when choosing a sunscreen.
Achieved Vs. Labeled SPF
SPF stands for Sun Protection Factor and every sunscreen has one. The SPF number indicates not just how long, but how well the product protects volunteers with white skin from developing a sunburn. Yes, with a higher SPF it will take longer to burn but the degree of protection also depends on the strength of the sun, which varies a lot. For example, the same amount of solar energy in one hour of sun exposure at 9:00 AM could strike our skin in just fifteen minutes at 1:00 PM on the same day.
The FDA requires that all manufacturers must apply the same standard amount of sunscreen to skin when they perform testing to determine the SPF value of the product. This standard amount (or dose) is 2 mg/cm2, which is considerably more product than most people feel comfortable using. As a result, people usually do not apply a sufficient amount (dose) of sunscreen to achieve the SPF that is listed on the product label. In fact, the average person only achieves 1/3 or less of the labeled SPF. It can even be much less than that if the product is applied sparingly, for example with a light mist of a spray sunscreen.
Studies that show negligible added benefit from using SPF 50 compared to SPF 30 have been done under laboratory conditions with the standard applied amount. This does not translate well to the real world where people apply less. Using a higher SPF product can partly compensate for applying less than the standard amount. Many people would prefer this approach compared to applying 2 mg/cm2 which can seem to be an unpleasant excess.
Strategies to achieve good protection include choosing a Broad Spectrum product with a high SPF (nothing less than 30) and it should be applied generously, preferably as two coats which will help to prevent missing a spot.
Product Accuracy
In the United States, the FDA, through its over-the-counter (OTC) drugs division, governs which minerals and chemicals are allowable as active ingredients, and also sets rules that manufacturers must follow in producing, testing, and labeling sunscreen products. We are not aware of the FDA or any other government agency conducting routine surveillance to ensure that sunscreen products accurately reflect the labeled SPF value. However, this has been done by the nonprofit organization, Consumer Reports. According to their 2020 report, CR found that 2/3 of the 53 products they tested actually provided less than half of the SPF that was labeled on the bottle. Their results have not been independently verified but assuming they are true it is certainly very disappointing that we can’t completely trust the accuracy of the SPF value with every brand of sunscreen. Suggestion: select a higher SPF regardless of the brand.
Sunscreen Vs. Environment
Concern has been raised about the possibility of certain sunscreen chemicals, such as oxybenzene and octinoxate, contributing to the bleaching and demise of ocean coral or causing hormonal problems for aquatic animals. Under experimental laboratory conditions, toxicity can be shown at high levels, however measurements of the amount of sunscreen actually present in ocean water in Hawaii and the Virgin Islands is far lower than the level reported to be toxic in the lab. Subsequent studies demonstrated that warmer water temperature causes coral bleaching so the main problem appears to be global warming rather than sunscreen chemicals. This is an area of emerging science and is certainly deserving of further study. What has indeed been well proven is that sunscreen can reduce the risk of skin cancer in humans. The public health implications of restricting its use should be taken into account, and further research conducted, before banning a proven skin cancer prevention tool.
Absorption Into The Body
Recent research revealed that measurable amounts of sunscreen chemicals can be detected in the blood after very heavy use. In the study, participants applied sunscreen at a full dose of 2 mg/cm2 to 75% of their body 4 times per day for 4 consecutive days. That’s a lot of sunscreen! Until this study was done, these chemicals had been considered “Generally Regarded As Safe and Effective” (GRASE). Now, the FDA is retracting the GRASE designation until additional research can actually prove them to be safe.
Despite demonstrating their absorption, the FDA does not claim that these chemicals are unsafe. Due to the proven benefit of sunscreen in protecting against skin cancer, the FDA has made it clear that they do not advise anyone to refrain from using sunscreen while further study is conducted to confirm that it’s safe.
Sun Safety for Kids recommends the use of long clothing, rashguard-style swim shirts, hats, and shade as equal or better sun protection measures. Compared to slathering 75% of the body with sunscreen, taking these other common sense measures will greatly reduce the area of skin in need of sunscreen, and the amount that could be absorbed.
FDA "Standard" Dose
In case you wish to apply the FDA standard amount of sunscreen that the manufacturer was required to use in determining the product’s SPF value, specifically 2 mg/cm2, it requires approximately 1 teaspoon (5 ml) of product applied to each of 9 body areas.
If wearing a traditional bathing suit and needing to treat all 9 body areas, it would require 9 teaspoons = 3 Tablespoons = a 1-1/2 oz shot glass (jigger) of sunscreen.
But, if covered up, 1 teaspoon will be sufficient for the face, ears, and neck. (Don’t forget the back of your neck.) Just a little more will take care of the backs of the hands, wrists, and the decolletage area of the mid upper chest. Thanks to a little clothing, that’s less than 2 teaspoons, compared to 9 for the whole body.
Substantivity and Photostability
The ability of a product to stick to its target is its substantivity. Sunscreen works best when it sticks to the dead cells on the surface of the skin, absorbing incoming UV radiation before the UV penetrates down to the basal (bottom) layer of the epidermis where it could cause a mutation leading to cancer. Factors such as absorption (see above), rubbing, sweating, or washing-off lead to a reduction in the amount of sunscreen remaining on the skin surface over time.
Photostability refers to how well the sunscreen behaves after it has already absorbed some UV. Sun exposure can degrade some sunscreen ingredients which weakens their ability to continue absorbing UV.
These are among the concerns for why it is generally recommended to reapply sunscreen every 2 hours for best results. While it’s not a bad idea to get in the habit of applying sunscreen every morning, this cannot be guaranteed to continue providing sufficient protection when UV levels peak between 10 a.m. and 4 p.m.
Some schools have not accounted for substantivity and photostability when they assume it should be good enough just to apply sunscreen at home before coming to school. Children must be permitted to use sunscreen at school.
Application to Children
Sunscreen is indicated for use on children 6 months of age and older. Infants younger than 6 months should be physically protected from the sun by their parents.
During early childhood, parents will have to do the application but before long impatience and resistance from the child can be expected. Parents must sometimes get creative in finding ways to avoid a struggle and gain the child’s cooperation. Being a role model and letting your child observe you using sunscreen can help.
The goal should be to teach children how to take charge and do the application themselves so that by the age when they start school they will already be self reliant. Some teachers will supervise or assist with sunscreen application upon written consent from the parent, but many teachers do not want to be involved.
Parents, teachers, and children alike will quickly realize that a hat and long clothing go a long way toward reducing the amount of sunscreen needed and the length of time to apply it.
Spray Sunscreen Problems
While a spray product can be ideal for use on hairy areas of skin, there are concerns. Some people use it like cologne, applying just a light spritz and achieving only a tiny fraction of the labeled SPF value, not to mention missed areas of skin with resulting SPF of zero and high risk of sunburn. Also, there are concerns about inhaling the sunscreen chemicals so it should not be applied indoors. The latest concern with aerosol sunscreens is the degradation of the propellant to produce benzene. Benzene is a carcinogen that can cause leukemia and more is produced when a product gets old or becomes warm (like at the beach in summer). While benzene has been detected in spray products it is generally not found at a dangerous level in either chemical or mineral sunscreen lotions.
Sunscreen Allergy
Not all allergies are alike. Allergic (hypersensitivity) reactions fall into two broad categories: acute and delayed.
Allergies to peanuts and penicillin are in the acute hypersensitivity category. These are the potentially very sudden and serious reactions that can cause hives, asthma, or life-threatening anaphylaxis, and when a severe reaction occurs it may be treated with an Epi-pen.
By contrast, allergic reactions to sunscreen are of a completely different, less serious type known as delayed hypersensitivity or allergic contact dermatitis. The result is an eczema type of rash. It is itchy and annoying but not life-threatening, and can usually be treated with a steroid cream. When someone does develop an allergy to sunscreen, it is usually possible to simply find another sunscreen product, such as perhaps a mineral sunscreen, or another one lacking the specific chemical to which that person has become allergic as determined by allergy patch testing.
Allergy Testing
In case a person is suspected to be allergic to sunscreen, they can conduct a “usage test” with it. Apply a small amount of the product on a spot about the size of a dime on a sun-exposed area of skin, such as the side of the neck above the collar. Unless a rash develops at the test site (in which case the test should be aborted) re-apply the product every day to exactly the same little spot for 4 consecutive days. If, during or shortly following the test period, a rash occurs at the test site, that is considered a positive test and the individual almost certainly is allergic to the tested product. If no rash has developed by several days after testing, the product can probably be used as directed. This same procedure can be used to test other skin products prior to using them in a normal fashion.
Sunscreen At School
Some school administrators have objected to providing or even allowing sunscreen use at school on the grounds of it possibly causing an allergic reaction. That is not a reasonable concern. Sunscreen allergy is uncommon and when it does occur it results in contact dermatitis but not the serious acute allergic reaction caused by ingesting peanuts, for example. In case a student has developed a sunscreen allergy, the case should be handled similarly to a child that has become allergic to the liquid hand soap supplied in the school’s restrooms. An affected student can simply bring their own well-tolerated sunscreen product to school rather than using whatever the school might provide.
Sunscreen vs. Vitamin D
Studies have shown that sunscreen, when it’s applied correctly, can reduce the amount of vitamin D that the skin will produce upon sun exposure. Other studies have show that “sunscreen users” do not suffer more vitamin D deficiency than non sunscreen users. This is probably due to not using high SPF sunscreen consistently and sufficiently.
Make skin cancer prevention your target. Effectively keep the sun out of your skin by always covering up and using sunscreen on exposed areas. Then, ensure that vitamin D needs for yourself and your family are met by taking a vitamin D supplement. Read more on our Vitamin D Page.
Sun exposure effectively produces vitamin D, but at the expense of increasing the risk of skin cancer.
References
- https://www.aad.org/media/stats-vitamin-d
- https://ods.od.nih.gov/factsheets/VitaminD-Consumer/
- Holick MF. Vitamin D Status: Measurement, Interpretation, and Clinical Application. Ann Epidemiol. 2008 Mar 10;19(2):73–78.
- https://www.endocrine.org/clinical-practice-guidelines/vitamin-d-for-prevention-of-disease
