Mineral versus Chemical sunscreens

Understanding sunscreens is easy – if we know where to start!  Let's begin with the UV filter that is responsible for ensuring that your sunscreen, in fact, works.

A sunscreening agent is any ingredient in your sunscreen, that is able to filter out sunlight in a measurable, repeatable, reliable way. (I say sunscreen filters now, because till about 10 years ago, the focus was mostly on the UV spectrum of sunlight. So we used to call these substances as UV filters. But now, since Indian skin needs protection against the entire spectrum, we have gently moved to the terminology: sunscreening agent, or sunscreen filters.)

These substances are an elite group within the domain of cosmetic chemistry, because they are made to deliver fixed outcomes, which would be measured using metrics like SPF, UVA-PF, critical wavelength etc. We will discuss these soon.

For now, let us start with the biggest question out there:

What’s the difference between organic and inorganic sunscreens?

Just one, structurally speaking: Carbon atoms.

If you remember your high school chemistry, anything with a hydrocarbon bond was included in the organic chemistry part of the syllabus, and materials without this carbon hydrogen bond were part of the inorganic chemistry section. 

The organic in organic sunscreens, does not refer to a plant base, or a natural source, but is simply a chemistry term to indicate the presence of hydrocarbon atoms.

Let us look at the chemical formula of  Zinc and Titanium oxides.

Zinc sunscreen filter is chemically, ZnO and titanium is TiO2. s you can see, no hydrocarbon (H or C symbols) in either of their structures, which means that they come under inorganic chemistry. Which is why mineral sunscreens are also called as inorganic sunscreens. But since most of zinc and titanium is mined from the earth, they are actually considered natural materials and physical sunscreens, despite how we feel about the ‘inorganic tag’.

There are just 2 mineral sunscreens at present, in contrast, there are 30+chemical sunscreen filters.

A typical structure, let’s take the widely used and notoriously in news, oxybenzone aka Benzophenone -3 , whose formula is C14H12O3, looks like this.

Right away, you can see the C in the formula and you can also identify the benzene ring structure in the image – which is usually a C6H6 (six carbon atoms with 6 hydrogen atoms) configuration. So you know that this molecule contains hydrocarbons, and as per our discussion here, and your high school chemistry in the years past, becomes an organic chemical! Which is why chemical sunscreens are also called organic sunscreens. 

Are organic aka chemical sunscreens natural?

No. Since most of the chemical sunscreen filters are ‘synthesized’ from petrochemical starting materials, cosmetic chemistry would classify them as synthetic sunscreens, or non natural materials.

If you are clear with the classification, we can move on to looking at how mineral and chemical sunscreens differ(do they?) in the way they protect us from sun in the upcoming post.

Topics you may like:

1. Why sunscreen?

2. Sunscreens for special circumstances