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Here’s a pet peeve of mine: SPF drops and boosters. Fellow skincare fanatic Hannah (@ms_hannah_e on Instagram) reminded me about them recently, right when I was in a ranty mood, so it fit right in.
What Are SPF Sunscreen Drops?
SPF Sunscreen Drops are products that you’re supposed to mix into other products to “turn them into sunscreens”. Some examples are:
- Dr Barbara Sturm Sun Drops SPF 50: $145 USD for 30 mL
- Coola Full Spectrum 360° Sun Silk Drops SPF 30: $46 USD for 30 mL
- (and to a lesser extent) Dermalogica Solar Defense Booster SPF 50: $48 USD for 50 mL
Why would you use these? Sunscreens often have horrible textures, so why not turn a product you already like into a sunscreen by adding some sunscreen drops into it? Not so fast…this ain’t a rant post for nothing.
Why I Hate Sunscreen Drops
Reason 1: They don’t deliver the protection they suggest
See that SPF number? It looks nice and high… but that’s the protection you’ll get if you apply the undiluted product directly on your skin like a regular sunscreen, with 2 mg of product applied per square centimetre of skin. On my face, that translates to about 3/4 of a quarter teaspoon.
So let’s work out the SPF protection if these sunscreen drops are used as intended.
- Studies have found that most people only apply half to one-fifth of the amount of sunscreen they should apply, even when they’re told to apply it generously. If they’re applying a non-sunscreen product, we can expect that they’re probably going to apply even less.
- SPF also scales approximately linearly with the amount you apply. For example, applying half of the ideal amount will give you around around half of the SPF protection.
So as an estimate, for my 381 cm2 face:
- If the drops are mixed in equal proportions with a product, and half the proper sunscreen amount is applied: ¼ of the labelled SPF = SPF 7.5 for SPF 30 drops, SPF 12.5 for SPF 50 drops
- “A few” drops mixed into a product (3 drops at 0.05 mL = 0.15 mL = 0.15 g = 0.39 mg/cm2): 0.195 (around ⅕) of the labelled SPF = SPF 5.85 for SPF 30 drops, SPF 9.75 for SPF 50 drops
Related post: What Does SPF Mean? The Science of Sunscreen
These SPF values are very low – so low that Australia’s Therapeutic Goods Administration wouldn’t let them say that they can help prevent skin cancer.
(While the products say that you can use them without mixing for maximum sunscreen protection, the marketing and dropper packaging encourages using a small amount mixed into a different product. Dermalogica is the best of the three – they say to use Solar Defense Booster on its own or mixed in equal parts with another product, but both Dr Sturm and Coola encourage the use of “a few drops” or “several drops”.)
Related post: Video: All Your Sunscreen and Make-up Questions Answered
But it’s better than nothing, right?
Um… not necessarily. Studies have found that people stay in the sun longer if they think they’re protected with a sunscreening product, and end up with more sun damage overall.
Reason 2: They’ll Give Patchy Protection
Another issue with these – sunscreen protection isn’t just about the amount of active ingredients. It’s about a ton more: how the active ingredients are distributed in the sunscreen, the “inactive” ingredients, how the different ingredients interact with each other, how the sunscreen applies on the skin, how it dries on the skin, and so on. Sunscreen is one of the most difficult products to formulate because changing almost any small thing will change the final SPF measured when tested.
One of the big factors that affects protection is whether or not a sunscreen forms a continuous film that spreads the ingredients evenly across your skin. Even with the same amount of sunscreening ingredients, products will deliver different protection if they spread differently.
Related post: Why Do I Need to Apply Sunscreen Before Sun Exposure?
That’s the big problem with essentially DIY-ing a sunscreen with these drops, as I’ve discussed before in my DIY sunscreen video. There’s no guarantee that the sunscreen drops will be mixed into the other product evenly. Since I’m guessing no one is spending more than a few seconds mixing their products together, it most likely won’t be even, meaning it’ll give patchy protection that’s probably thinner in spots.
But honestly, it probably won’t be much of an issue since the protection they’re giving is so low anyway.
(I have a theory that Dr Sturm’s Sun Drops are her secret ploy to trick people into not using sunscreen, since she “almost never” wears sunscreen and thinks it’s unnecessary. )
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