What Is Zinc Oxide? What Percentage of Zinc Oxide Should Be In Sunscreen?
In an attempt to safeguard marine life and protect coral reefs, many manufacturers of skin care products have started to launch their lines of biodegradable sunscreen. Zinc oxide is one of the main active ingredients in these lotions, and the questions arise spontaneously: what is zinc oxide? Is it harmful? What percentage of zinc oxide should be in sunscreen?
Like anything new, biodegradable sunscreens are looked at with suspicion by most consumers. In this article, we will tell you what zinc oxide is and why its presence in sunscreen shouldn’t concern you.
What Is Zinc Oxide?
Zinc oxide is a natural mineral consisting of the metal zinc that has been oxidized. Although zinc oxide occurs in nature, the mineral is quite rare. That’s why most cosmetic brands use mined zinc to produce purified zinc oxide in their laboratories.
The main benefit of zinc oxide is its capacity to block all types of harmful UV rays, including UVA, UVB, and UVC. This property has made it a key ingredient in mineral – or biodegradable – sunscreens.
Due to its many benefits, zinc oxide is also an active ingredient in many other skin care products including makeup products such as blemishes and lip balms, powders, ointments, and diaper rash creams.
How Does Zinc Oxide Block Sunrays?
Zinc oxide is defined as a physical blocker of UV rays. This active compound present in biodegradable sun lotions sits on your skin and forms a protective barrier against the harmful rays. Unlike the chemicals present in regular sunscreens, zinc oxide is not absorbed into the skin, and it is effective right after application.
The only downside is the white color the product leaves on your skin upon application. In fact, the zinc oxide particles often leave a white patina on the skin, and that’s one of the reasons many people prefer regular lotions.
To counteract this trend, many manufacturers have started to use nanoparticles of zinc oxide which remain clear on skin.
While there has been some debate regarding the safety of these particles, studies suggest they are perfectly safe to use in creams and lotions. Scientific literature shows that particles larger than 30nm do not get absorbed into the skin nor enter the bloodstream, posing no threat to human health. Most manufacturers of biodegradable lotions use either non-nanoparticles or nanoparticles greater than 30nm in their products.
When these particles aggregate into the substrate they form non-nanoparticles that stay clear when applied, so you won’t have to worry about the lotion’s whiteness.
However, if protecting the environment is one of the reasons you’re thinking to switch to biodegradable sunscreen, know that nanoparticles smaller than 35nm can be toxic to marine life. Due to their extremely small size, these particles may generate oxidative stress and potential cellular damage to corals, juvenile fish, and invertebrates.
With this in mind, our advice is to opt for a non-nanoparticle zinc oxide sunscreen.
What Percentage of Zinc Oxide Should Be In Sunscreen?
There are endless polemics regarding how much is too much zinc oxide in sunscreen. The cause of these debates is the lack of clear regulations and studies that show what amount of mineral to use to achieve the desired level of protection.
Due to this reason, some dermatologists and cosmetic brands promoting regular sunscreens have concluded that biodegradable lotions might be ineffective. However, this is far from the truth.
Although harmful chemicals are more effective in blocking UV rays, it has been shown that minerals such as zinc oxide and titanium dioxide still effectively block the UV radiations when used in cosmetically acceptable concentrations.
The actual concentration depends on whether the lotion has one or two active ingredients.
Biodegradable sunscreens containing only zinc oxide as an active ingredient provide adequate protection at concentrations above 15%. This concentration corresponds to an SPF of 24, which is on the lower side but still ideal for people with darker skin.
Concentrations between 15 and 20% correspond to an SPF of up to 32. Higher concentrations of up to 25% are cosmetically acceptable for lotions with an SPF higher than 32. However, a concentration of over 25% of zinc oxide not only is not cosmetically acceptable, but it would alter the texture of the lotion making it unpleasant on the skin.
To increase the SP factor of their lotions, many manufacturers use both zinc oxide and titanium dioxide as active ingredients.
In this way, cosmetic brands have managed to reduce the concentration of both minerals and increase the UV protection factor of their sunscreens. Many renowned brands propose biodegradable sunscreens that contain less than 10% of zinc oxide while providing an SPF of 50+, thanks to the association of this mineral with titanium dioxide.
Is Zinc Oxide Harmful?
No, zinc oxide is not harmful to humans. The mineral has a low overall hazard, and there are no restrictions regarding its use. There have been reported sporadic cases of allergies and respiratory toxicity related to aerosolized products.
Skin allergies triggered by ointments and lotions containing zinc oxide are very rare. Furthermore, zinc oxide has a wealth of additional benefits.
According to a study published in the Journal of Drugs in Dermatology, zinc oxide can regulate sebum production, reduce acne associated inflammation and eventually treat acne. This mineral can also treat rash and skin irritation, including diaper rash.
Besides, zinc oxide can prevent bacterial infections, and it has anti-aging properties, improving the healing of tissue damage.
Zinc oxide is a harmless mineral able to provide UV protection and not only. Studies also suggest non-nanoparticles of zinc oxide bring no harm to plant and wildlife, including coral reefs.
Replacing your regular sunscreen with a biodegradable one containing zinc oxide or zinc oxide and titanium dioxide is a great way to reduce skin cancer risk, lower the risk of skin allergies to sunscreen, and protect the environment. The white patina and slightly higher cost are well worth the investment.