DIY Sunscreen Isn’t Giving the Protection People Think It Is

A friend in cosmetic formulation tested a homemade zinc sunscreen at an FDA-accredited lab and the results were rough. The recipe was the same one all over TikTok and Pinterest: 25% non-nano zinc oxide blended into oils and butters with an immersion blender. On paper, people assume that means high SPF.

Actual test result? SPF 13 before water exposure, SPF 7 after the standard water-resistance test.

The issue isn’t zinc itself. It’s dispersion. Without industrial high-shear mixers and proper dispersants, the zinc doesn’t spread evenly across the skin. You end up with random patches that are protected and random patches that basically aren’t. The average protection ends up way lower than people expect.

I get why DIY sunscreen sounds appealing. Some people want fewer ingredients, others want to save money, and some just like making their own skincare. But sunscreen is one of those products where formulation matters more than the ingredient list alone.

If you want mineral sunscreen, stick with brands that actually do validated SPF testing. And please be careful handling loose zinc powder at home too, because inhaling fine particles is not something you want.

Anyone here actually tried homemade sunscreen before and noticed issues with burning or uneven tanning?