Chemistry of Sunscreen

Stop by a Wallgreens or CVS and you’ll notice a large sunscreen selection, but each product has advantages and flaws. The differences, it turns out, depend on the chemistry of each active ingredient. If you’re in the United States, glancing at the list on the back of each bottle, you’ll see that products tend to have some combination of 8 common active ingredients.

But did you know that of the 8 most common active ingredients, there are actually only two different UV protection mechanisms? Categorized below, you’ll notice that UV filter compounds are much more common, while the mineral blocker type only include two of the main compounds.

Sunscreen lotion contains active ingredients that contribute to the sunscreen’s SPF, protecting you from sunburn by keeping UV rays from reaching your skin and damaging cells. Active ingredients protect you from UV rays in two unique ways:

Filtering:

This method filters or absorbs UV light, turning the radiation into heat energy, rather than allowing it to cause cell damage.

UV filters chemical ingredients: Avobenzone, Homosalate, Octisalate, Octocrylene, Oxybenzone

  • Hazards of UV filters:
    • UV filters can and have been measured in blood of people who use sunscreen frequently. The main concern with these chemicals is endocrine disruption.
    • Oxybenzone is by far the most dangerous chemical found in sunscreen. It penetrates the skin easily and enters the blood stream. It has the ability to penetrate the blood-brain barrier, causing hormone disruption. It is estrogenically active and has potent anti-androgenic effects.

Blocking:

Blocks UV light from penetrating through the mineral ingredients in the sunscreen so that it never comes into contact with your skin. (ex. Zinc Oxide and Titanium Dioxide)

Pick up your tube of sunscreen and look at the back. You’ll see a number of active ingredients. Typically, you’ll see 4 or 5 Filtering type ingredients listed. The compounds that protect by Filtering will tend to absorb only certain wavelengths of light, so sunscreen companies include a combination of different ones to block a broader spectrum of UV rays.

Blocking type ingredients work in a different way, so they are present either by themselves or with a few filter ingredients. For example, you might have sunscreen that lists zinc oxide as the only active ingredient.

To avoid sunburn and more importantly skin damage from UV rays, elect for a broad-spectrum sunscreen with as high an SPF as possible, and ideally use a sunscreen that also contains Zinc Oxide or Titanium Dioxide.

UV blocking minerals: Zinc Oxide, Titanium dioxide

  • Hazards of mineral blockers:
    • Zinc Oxide and Titanium dioxide particles are photoactive, meaning they can create free radicals when exposed to UV radiation that damage surrounding cells. To mitigate this risk, manufacturers apply surface coatings to these particles.
    • Both of these mineral blockers are electrically charged molecules. Over time and due to heat exposure, these mineral blockers can settle or clump, leaving gaps in skin coverage. To be effective, mineral sunscreens contain ingredients that hold zinc oxide or titanium dioxide in a suspension to provide an even coating on the skin.
    • Titanium Dioxide creates more free radicals that do oxidative damage to your body and skin cells, and increases aging processes. Zinc oxide tends to have a broader-spectrum range of coverage than titanium dioxide, although the combination of both Zinc Oxide and Titanium Dioxide provide the broadest range of protection.
    • Zinc and titanium oxide may potentially harm environment.

Some products, such as “SheerZinc Face” by Neutrogena, will contain zinc oxide. Finding a product that contains both zinc oxide AND titanium dioxide is much less common due to the highly charged particles tendency to coagulate and cause clumping.

Conclusion:

As discussed, there are two different types of sunscreen. If you are going for a product that contains Mineral Blockers, Zinc Oxide is preferred over Titanium Dioxide. Check products that contain mineral blockers to ensure lotion consistency is homogenous and not de-coagulated because the clumps will cause gaps in skin coverage, thus causing you to get burnt.

Your ideal sunscreen might have the following active ingredients:

  • Homosalate (8–10%)
  • Ocinoxate (variable percentage)
  • Octocrylene (2–6%)
  • Zinc Oxide (5–15% +)

 

One comment

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

This site uses Akismet to reduce spam. Learn how your comment data is processed.