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  • Writer's pictureShayna Keller

How to Decode Sunscreen to Prevent Skin Aging

Sun protection devices

By 2024 it is projected by the Transparency Market Research that sunscreen will be a $24 billion industry and confusion in the consumer is overwhelming. Which sunscreen? Does SPF really matter? How much do I need and when do I need to reapply? Are there ingredients that are potentially harmful to my health?

Regardless of the confusion, we all have skin, and we need to take care of it if we don’t want to age too quickly or increase our risk for skin cancer. 

It is okay to be a little vain ;) 

In this post, I will be discussing how to read a label from a marketing perspective, why we need sun protectants, how much to apply, when to reapply and a brief discussion on hormone-disrupting chemicals in some sunscreens. Finally, I will discuss an after sun exposure regime that keeps my skin happy and hydrated after a day in the sun!

Definitions and Labels

Sunblock – physically blocks UV radiation by reflecting the Sun’s rays, typically using zinc oxide and or titanium dioxide. Often leaves a white cast on the skin that may be unappealing. Sunblock is considered safe and effective by the FDA. Best for babies and people with sensitive skin.

Sunscreen – chemically blocks the UV radiation by absorbing and converting the Sun’s rays, typically using one or more of about 12 different FDA-approved - UV filtering agents. 

UVA radiation - Radiation that contributes to DNA damage, skin aging and skin cancer (Siller et al, 2018)

UVB radiation – Burning radiation (Siller et al, 2018)

Broad-spectrum – protects against both UVA and UVB radiation

SPF – Sun Protection Factor

Water-resistant – the sunscreen takes twice as long to rub off your skin in the water as regular sunscreen; reapply every 60-80 minutes

Sensitive skin – indicates the use of minerals like zinc and titanium rather than chemical sunscreens

Purpose of sunblock/sunscreen

The goal of using sunblock and sunscreens is to prevent skin cancer and sunburns. Historically sun care has primarily focused on UVB radiation but not UVA radiation (Siller et al, 2019). Unfortunately, skin cancer is still on the rise by 3-6 percent in most countries even though awareness of skin protection continues to increase (Nijsten, 2016).

How to Naturally Increase Melanin 

At the same time every day ideally before peak UV ray time, say 8 am and sit or lie in the direct sun. For people that burn easily I would say no more than 10 minutes TOTAL. For others that take a bit longer to burn no more than 20 minutes TOTAL. So flip over accordingly. Day by day you are exposing your skin to the benefits of the sun (Vitamin D synthesis, immune support, warmth etc.) to help build up your melanin content without burning first. This helps to prevent burns on those longer days of the summer that you are outdoors recreating. 

SPF Breakdown

Major confusion seems to occur with SPF and the thought tends to be the higher the better, but that is not the case. In the graph below I break down the SPF numbers, percent of UVB blocked and compare it to people that are easily burned, like myself and others like my partner that take a little longer to burn without sun protection.

interpretation of SPF table

Fig. 1 from Tachibana, 2010 and Nijsten, 2016

SPF rating is in the far-left column. Right around SPF 

30-50 the % of UVB blocked is about as much as it will get. Anything >50 SPF is buying yourself a falsesense of security.

Spectrum of UV Protection

Understanding the different types of UV rays from sun exposure in addition to the types of chemicals used in sunscreen and the minerals used in sunblock is critical to getting the most bang for your buck! As you can see in the chart below that most sunscreens are poor UVA protectants. UVA rays contribute to aging skin such as sunspots, wrinkles and DNA damage. DNA damage is the main factor in skin cancer development. So that being said we need to make sure we have a broad-spectrum sun protectant on exposed skin. This is why many sunscreens and sunblock have multiple chemicals and or minerals in them. 

Different of sunscreen ingredients

Fig. 2 Types of sunscreen and sunblock ingredients in relation to their UV ray protection benefits. Note about the European Commission

The EC has deemed those * chemicals as unsafe above a certain concentration in products.

Application of Sunscreen and Sunblock

For adults we should be using about 3 tablespoons (1.5 ounces) on our exposed skin:

  • 1 teaspoon on face and neck (remember ears)

  • 1 teaspoon on each arm (or 2 teaspoons total)

  • 2 teaspoons on chest, belly and back (don’t forget the upper shoulders)

  • 2 teaspoons on each leg (or 4 teaspoons total)

We should be reapplying every 1-2 hours and if you are using sunscreen it needs to be applied 15-30 minutes before your expected sun exposure for maximum protection. This means that a 6-ounce bottle should only last a short while if we spend quite a bit of time outside in the direct sun.

If you are sweating or playing in the water reapplication of the sunscreen will need to be every 40-80 minutes. It is important to note that reapplication of sun protectant doesn’t mean you are protected for the whole day. Remember that water-resistant does not mean water-proof. You still need to reapply sunscreen. There is no such thing as water-proof sunscreen, that’s marketing BS. 

Physical Sun Protectants

Even the American Academy of Dermatology recommends seeking shade, wearing lightweight long sleeve clothing, wide-brimmed hats and sunglasses. This is my preferred way to protect my skin and ends up being less expensive in the end compared to buying a dozen bottles of sunblock a year. I burn pretty easily living in Colorado, so for me, it’s best to just cover up. 

One of my favorite companies for lightweight super soft sun protection is Free Fly Apparel. They make their clothing with bamboo too! Most outdoor companies have a line of lightweight summer clothing to protect yourself from the sun. 

UV Ray Index

I encourage folks to avoid direct sun exposure during peak UV rays hours between 10 am – 3 pm especially those of us that burn easier than others or work outside. If the UV index is above high I recommend covering up with lightweight clothing rather than trying to deal with sunblock and sunscreens. 

Check out for daily updates on the UV index in your area.

Harmful to Human Health?

Oxybenzone is by far the most common sunscreen on the market. The FDA allows products to contain up to 6 percent of oxybenzone. The European Commission has created an upper limit on this chemical filter of 2.2 percent because of the amount in which the body absorbs. Oxybenzone is likely an endocrine disruptor in humans. This means it negatively impacts our hormonal, or endocrine system. Today it has been identified in urine, sweat and breast milk (Siller et al, 2018). I recommend to my patients/clients to avoid sunscreens with oxybenzone. We have enough exposure to endocrine-disrupting compounds that if there is any indication that something may be less than safe, we should not be using it.

Sunscreen Bans

Interestingly Hawai’i banned the sale of any sunscreen containing oxybenzone and oxtinoxate, which took effect in January 2021 (Scanlon, 2021). The ban was implemented to protect Hawai’i’s native coral reef ecosystems. Palau, Aruba, Bonaire and US Virgin Islands have also followed Hawai’i’s efforts to protect their coastal ecosystems and hopefully decrease the rates of coral bleaching (death of the coral reefs). According to the paper titled Sunscreens cause coral bleaching by promoting viral infections, within 20 minutes of being in the water about a quarter of the sunscreen used on a person’s body is washed off into the ocean. It then accumulates in the sensitive coral reef ecosystems and has a negative impact on the health of the ecosystems. Interestingly, Johnson and Johnson the producer of the Neutrogena argues that since the FDA deems both oxybenzone and oxtinoxate ‘safe’ that this ban puts people’s lives at risk.

After Sun Care

Not all ‘aloe’ is created equally. That weird electric green goo that comes in that giant bottle from your local grocer is NOT what I am talking about here. I am talking about the real deal, Aloe vera or Aloe the plant. You know the one your mom told you to use when you get a kitchen burn? That’s the one! 

Aloe for after sun care should be free from: 

in alcohol, fragrances (these are endocrine disrupters people), dyes, PEG or polyethylene glycol, urea, ammonia, or anything else that requires to have a chemistry degree to understand it’s ‘value’ in your after-sun care. 

My recommendation is Lakewood Organics Inner Fillet Aloe vera gel. I usually do not encourage the gel due to the thickeners like xanthan gum and guar gum BUT this is for your skin so it makes it a lot easier to apply to your skin. If you aren’t going back out into direct sun in the next 24 hours add some Lavendula spp. essential oil. Lavender helps to heal burned/damaged tissue.

Recipe for Aloe-Lavender Gel:

  • 4 ounces of aloe gel

  • 10 drops lavender essential oil

  1. Mix with a wooden stick

  2. Apply liberally to your body after direct sun exposure and apply more often if you have a sunburn. This is a time where MORE is better. So every time it dries, put more on your skin.

  3. Store in a glass jar with lid (mason jars work well)

  4. Keep in fridge for longer shelf life.

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