The legend of the sun | Lab Muffin Beauty Science

Here’s a growing directory of resources on sunscreen myths. They are written as fact rather than fiction, except where specifically stated. These are mostly secondary sources, either myself or other science communicators – most of the cosmetic science studies need to be interpreted in a subtle way to be useful.

Also check out this Sunscreen FAQ, and my Basic Skin Care Guide eBook that walks you through how to choose and use a sunscreen, as well as a cleanser and moisturizer.

Sun screen safety

All sunscreens are actually very safe

Chemical sunscreens (oxybenzone, octocrylene etc.) are very safe. They are some of the most scrutinized ingredients in consumer products.

Mineral nanoparticles are also very safe. Nanoparticles do not penetrate the layers of dead skin in intact skin.

Chemical sunscreens are safe during pregnancy

If they weren’t, there would be more warning labels on products, especially in countries where sunscreen is a drug like the US and Australia.

Chemical sunscreens are safe for children

Generally, sunscreens are not recommended for children under 6 months, not only because of the filters but also other ingredients. Much of this is due to the relative skin area of ​​children.

US FDA regulations

The FDA has not declared that chemical sunscreens are no longer safe – there are a proposed change in their GRSE status due to lack of data. This is intended to be a call for companies to provide data, in which case their GRSE status will be maintained. This is currently in limbo due to the ban on animal testing. However, similar chemical sunscreens have been certified as safe around the world through other methods, such as in the EU.

A study conducted by the FDA found that sunscreen chemicals are absorbed into the bloodstream, but this does not mean that they are not safe. The numbers were small, and it meant that more data was needed for them to maintain their GRSE status.

Endocrine disorders

“Potential endocrine disruptor” does not mean that something will disrupt your hormones to any significant degree. In the context of cosmetic ingredients, it usually means that it has been found to bind poorly to hormone receptors in test tube studies.

It is unlikely that low doses of chemical sunscreens will have a harmful endocrine disrupting effect (often called a “non-monotonic dose response effect” or NMDR – you may also see this myth stated as “dose NOT toxic for endocrine disruptors”).

Benzene contamination in sunscreens was not dangerous

Benzene was detected in some sunscreens (both chemical and mineral) in 2021 by Valisure, a laboratory involved in class action lawsuits and not known for accurate measurements. Even with their potentially high numbers, the amounts of benzene in sunscreens are not expected to cause any noticeable health effects.

Sunscreen ingredients

Mineral sunscreens do not reflect much UV

Mineral sunscreens generally (90-95%) work by absorbing UV and converting it to heat, like chemical sunscreens. Mineral sunscreens are not very effective, or safe for melasma, because of this.

SPF boosters

If a “100% mineral” sunscreen isn’t too white, it probably contains hidden chemical sunscreens (SPF boosters). These are almost identical to chemical sunscreens, but for esoteric regulatory reasons, they do not need to be listed as active ingredients. They are as safe as chemical sunscreens, but can cause reactions if you are allergic.

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Avobenzone does not need to be avoided in sunscreens due to its low strength – it can be fortified more effectively, such as in Neutrogena’s Helioplex formulas which retain 85% of UVA protection after 5 hours of sun exposure.

Allergies

About 1% of people are allergic to chemical sunscreens, not 25%.

Using sunscreen

Chemical sunscreens do not work with the skin to be effective

Chemical sunscreens you don’t need to absorb through the skin, or react with the skin, to work. They do not need to be applied to bare skin, and should be used OVER skincare, such as mineral sunscreens.

Chemical sunscreens work fast. The waiting time (usually 15-20 minutes) is for all sunscreens, so that they dry and don’t smear, and make sure you don’t expose your skin to UV while applying.

How much sunscreen should you apply?

There is no set number of “fingers” of sunscreen to use on your face, as the size of these “fingers” varies greatly. To get the SPF listed you need to use 2 milligrams of product per square centimeter of skin (the amount used in testing). 1/4 teaspoon (1.25 mL) is a good, generous serving for most people.

Do you need sunscreen?

Australia has up-to-date, evidence-based sun exposure guidelines that balance the benefits and risks of sun exposure. The latest version (2023) even takes skin tone into account. Most people should take sun protection measures (including wearing sunscreen) for skin cancer prevention purposes on days when the UV index is predicted to reach 3 or higher.

The reuse of sunscreen

All sunscreens need to be reapplied regularly. Many kilos of solar are photosensitive now, so the main reason for reuse is usually not the decomposition of ingredients due to UV exposure – the sunscreen film accumulates and wears off over time.

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SPF tests are standardized around the world

SPF is tested in the same way regardless of region. Most regions use the ISO 24444 method that involves human volunteers and a UV lamp, or a slightly modified version. This means that “SPF 30” in an Australian sunscreen is no more than any other sunscreen, and is not tested separately to take into account Australia’s high UV levels.

SPFs above 30 are good

SPF 50 is more effective than SPF 30, not just 1% more effective. SPF 30 only blocks 97% of erythemal (reddening) UV and SPF 50 only blocks 98% when the full amount is applied evenly. Inadequate and incomplete application means more UV passes through. This is UV related to organisms, and the ratio will be the same as the SPFs (ie SPF 50 will allow more than 3/5 of the amount SPF 30 does) if the same amount of sunscreen is used.

You can’t get an SPF rating from the percentage of active ingredients. Things like how the ingredients are distributed in the sunscreen, any SPF enhancers in the formula etc. they will change the protection of the final film.

SPF is not just a measure of UVB protection

UVA varies, slightly less than UVB

UVB contributes more to premature skin aging than UVA

Types of sunscreen products

Sunscreen sprays and mists do not provide much protection. Only about 1/5 to 1/9 of sunscreen sprayed on your face from 20 cm away will stay on your skin (for the sunscreens I’ve tested, you’ll need to use about 80-120 sprays to get the SPF listed on your face).

Sunscreen sticks

Sunscreens require multiple passes to provide adequate protection. The general recommendation of 4 passes doesn’t seem valid for current sticks – the 3 sticks I tried required 34 passes on average to achieve the stated SPF.

SPF lip products

SPF lip products are safe – tested for oral use, including whether or not to swallow.

Effect of environment

Sunscreen does not burn coral reefs

This was largely based on one dodgy study published in 2016 that was heavily promoted in the media (“science by media release”). A comprehensive 400-page review conducted by the National Academies in 2022 found that mineral and chemical sunscreen additives have an excessive environmental impact — mineral sunscreens are clearly not better for the environment, by any measure. The report concluded that the sunscreen ban is “premature” and not based on good data, and cited NOAA’s “Chemicals in Skincare and Coral Reefs” page as an example of bad communication.

Zinc oxide has more negative environmental effects than most sunscreens

Natural factors still have an impact. Zinc oxide has major impacts especially during production, and is classified as toxic to aquatic life.

A blue light

Blue light from the sun causes a long-lasting tan on darker skin tones

Mineral sunscreens do not protect against blue light

Colored products protect against blue light

Digital screens don’t emit enough green light to worry about. You don’t need to wear sunscreen in front of the computer, for example.