Last Updated on November 20, 2022
Here’s all you need to know about Zinc Oxide, an ingredient found in mineral sunscreens. It serves as your skin’s armor against UV rays.
The call to wear sunscreen on a daily basis is now more common than in the past. Yet, not a lot of melanated folks do. This article is part of an ongoing series on why black can crack, to help you understand why SPF is super important. So, read on to learn about this MVP ingredient called Zinc Oxide.
What is Zinc Oxide?
Zinc Oxide is an inorganic, molecular compound of Zinc (yep, the metal) when it interacts with Oxygen. Hence why its scientific formula is ZnO (Zinc + Oxygen). This synthetic compound is typically in a white powder form which makes it pretty easy to use as an ingredient.
What is Zinc Oxide used for?
You might know Zinc Oxide from sunscreens. But, it’s also used in a variety of products beyond cosmetics. When used topically in cosmetics, though, it serves many skin benefits.
For examples, you’ll find it in some baby powders and anti-rash ointments (treats rashes), anti-dandruff shampoos (treats dandruff), antiseptic creams (treat burns, sores and cuts), and, of course, barrier creams like sunscreen (protects from free radicals). Zinc Oxide is also used as a colorant, which is what gives mineral sunscreens their white color.
Why is Zinc Oxide used in mineral (physical) sunscreens?
Zinc Oxide is an anti-irritant as it protects your skin from UV rays, dirt and other environmental stressors. This makes it a great skin barrier agent in skincare, particularly mineral sunscreens in which it’s used as an active ingredient.
Think of ZnO as a physical barrier between your skin and the sun’s rays. A sufficient layer of mineral sunscreen containing Zinc Oxide will physically block rays from penetrating your skin. If your skin were to absorb UV rays without protection, the rays could form free radicals in the skin cells.
Free radicals can cause premature ageing, hyperpigmentation and, in the worst-case scenario, DNA damage that could lead to skin cancer. If the rays hit your epidermis (top layer of your skin) as well, it can cause sunburn which can also damage cells. Zinc Oxide helps to prevent these unfortunate events from happening.
Fun fact: Zinc oxide cannot dissolve in water. 💧
So, does that make any sunscreen with ZnO waterproof?
No, ‘water resistant’ or ‘water insoluble’ doesn’t always mean ‘waterproof’. ZnO might be water-resistant, but it can wash off when prolonged in water. It can also wash off if it interacts with different types of water such as sweat, salt water, chlorine water, and so on.
We spoke to board-certified dermatologist and owner of New Jersey-based Bergen Dermatology, Dr Naana Boakye, who confirmed that, “The FDA has made a rule that sunscreens can only be water resistant, not waterproof. Usually, there is a time limit of 40 mins or 80 mins associated” before your sunscreen starts to wear off.
What’s the ideal % of Zinc Oxide in a mineral sunscreen?
The U.S Food and Drug Administration (FDA) approved Zinc Oxide to be used in sunscreens at a concentration of up to 25%.
However, you might notice the percentage of ZnO in a mineral sunscreen can vary. The question, then, shouldn’t be “is X% in my sunscreen enough?” but “how stable is the ZnO in this sunscreen in terms of particle size, and is it well formulated to spread evenly and stay evenly-spread?”
To ensure stability, Dr Boakye advises to pick a non-nano sunscreen over a nano sunscreen. But, what are these? She says:
“Nano vs Non-nano zinc refers to the particle size of the Zinc Oxide. Zinc Oxide is the filter that blocks against ultraviolet light A and B. I prefer non-nano zinc particles. There have been some studies that have suggested that nano particles can be absorbed into the body.”
DR NAANA BOAKYE, MD, Bergen Dermatology
Nano ZnO are smaller in size than non-nano ZnO, which explains their ability to be absorbed into the skin. But, we don’t want that! So, the next time you go shopping for a mineral sunscreen, check that you’re picking one that’s formulated with non-nano Zinc. Also, make sure it spreads evenly and stays evenly-spread until you need to re-apply.
Note: ‘Nano Zinc Oxide’ is the same as ‘micronized Zinc Oxide’ on the label of your sunscreen. 🧴
One extra tip is that if the mineral sunscreen you like also has Titanium Oxide (another active ingredient in mineral sunscreens), make sure the percentage of the Zinc Oxide is equal to or higher than the Titanium Oxide. In this regard, Unsun Mineral Tinted Face Sunscreen Lotion SPF 30 is a SPF of choice for melanated skin tones.
What are the downsides of Zinc Oxide?
- Zinc Oxide in its natural form can be toxic if inhaled or swallowed. That’s why it’s safer when dispersed in carrier liquids like sprays, lotions, creams and oils, like sunscreen.
- Not only is nano ZnO not as safe on skin as non-nano ZnO, but it may not be planet-friendly as well as it may be toxic to sea life when ingested. So, it’s best to wear a non-nano ZnO mineral sunscreen if you want to swim in the ocean.
- Due to its white pigment, ZnO can leave a noticeable white cast, especially on dark skin tones. However, technology has come far that you can now get mineral sunscreens without the white cast. This is either because it’s got tint that can balance out the color, like Unsun Cosmetics’ Mineral Tinted Face Sunscreen, or the ZnO’s particles are smaller in size.
What are the upsides of Zinc Oxide?
- It provides broad spectrum protection from UVA1, UVA2 and UVB rays. This means it prevents cellular damage that leads to premature ageing (and potentially skin cancer) and protects from epidermal burns which may also lead to skin cancer.
- It protects from UVC rays. Although the sun emits UVC, the ozone layer blocks it so that it doesn’t actually reach Earth. However, UVC rays can come from other sources like lamps or lasers. Zinc Oxide helps to shield the skin from the free radicals that could ensue from these sources.
- You get immediate protection, so you don’t have to wait for 10-20 minutes after application before heading outside (unlike a chemical sunscreen).
- It’s safe to use on all skin types, including sensitive. It’s so safe, the FDA approved it for kids as young as 6 months old (even younger)!
FAQ
What does Zinc Oxide do for skin?
It generally provides barrier protection against irritants. This helps to promote wound healing as well as shield the skin from the damaging effects of environmental aggressors like sun rays.
Can you use Zinc Oxide for skin whitening/to treat skin discoloration?
No. It’s simply a barrier protectant and colorant agent.
Is Zinc Oxide in skincare safe for skin?
Yes. The FDA considers it a GRASE ingredient which officiates it as a safe and effective ingredient for use in sunscreens.
Can Zinc Oxide treat acne and acne scars?
No, Zinc Oxide cannot treat acne and acne scars. However, it’ll protect against UV rays which is one of the leading causes of hyperpigmentation in dark skin tones. So, SPF is a preventative measure, not a treatment.
Does Zinc Oxide work for sunburn?
Dr Boakye says that “if zinc oxide is applied properly to the skin, it can help prevent sunburns.”
CONTRIBUTING DERMATOLOGIST [WITH THANKS]:
Naana Boakye, MD, Bergen Dermatology (NJ)
Co-owner of Karité Shea Butter
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Disclaimer: As sunscreen is a therapeutic product, this article does *not* constitute health or medical advice. If you have any questions in relation to your health, please seek the advice of a dermatologist or general practitioner.