Category: Blog

… Basically I have a question about the last question you got. The person who asked mentioned that we’re required to use 1/2 teaspoon of sunscreen for the face alone and now I’m a little confused because I’ve thought that we “only” need 1/4 of a teaspoon? Or about 1.25 ml? Is that wrong? I’m sorry for asking, I’m just always worried about not using enough product to get the proper protection.

Great question, thanks for asking @naevery 🙂

It’s not right, and it’s not wrong…it depends!
Let me explain 🙂

The density of sunscreen used in SPF testing is always 2 mg/cm²

That means for every square centimeter or skin, 2 mg of sunscreen is applied.

This is easier to do when testing, because it’s done on the back where you can draw a 30 cm² square and apply 60 mg to it.

Figuring out the area of the face is trickier.

The ¼ teaspoon or ½ teaspoon or 1.25 ml are based on two estimates.

The first estimate is the average area of a human face, and the second estimate is the average density of a sunscreen. Remember that ml is a measurement of volume, it provides no information about weight.

Water at 4°C has density of close to 1. 1 ml of water will weigh about 1 mg. However, oil for example has a lower density, 1 ml of oil won’t weigh 1 mg, it might weigh 0.8 mg (depending on the type of oil).

That makes things more complicated, because you can’t assume that 60 ml of sunscreen will weigh 60 mg, it might weigh 65 mg or 55 mg.

So the ¼ teaspoon, or ½ teaspoon are just estimates for an estimated human face, and an estimated sunscreen density.

These researchers for example used a beer bottle cap to measure out sunscreen.

So in order to know how much sunscreen, exactly, to apply you’ll need two measurements. The density of your sunscreen, which you can take by measuring out, say, 10 ml of sunscreen then weighing it. You’ll probably want a jewelry scale that has 0.001 g accuracy, and to measure a few times and average your measurements!

Finding out the area of your face is more difficult.

There are studies where people are told to apply sunscreen, and how much they’ve applied is weighed. It usually ranges between 0.5-1.5 mg/cm², when they’re unprompted about applying 2mg/cm². Their recommendation is to have people apply their sunscreen twice, instead of worrying about ¼, ½ teaspoon.

It’s up to you to how you decide to apply your sunscreen. Whether it be weighing it, measuring out the volume, or applying it twice, it’s better to err on the side on more for sun protection!

For Reference: ml = milliliter, mg = milligram, cm = centimeter, g = gram, and 1 mg = 0.001 g

Hope that helps!

…foundations, BB and CC creams. I see that they’re rated as highly as the straight sunscreens/sun creams. Theoretically, if we used the required 2mg/cm² (1/2 tsp) of these products for the face, will they give the same level of protection as the straight sunscreens/creams? I’m asking because I’m wondering if I could be relying on a watery serum foundation for the entirety of my sun protection.

Yup! Anything that has an SPF is tested the same way.

While the US FDA, Colipa/ISO methods have a couple differences, it is always at the density of 2mg/cm².

As long as it has an SPF rating, and you’re applying it at that density, you can be assured you’re getting that SPF – whether it’s called a serum, moisturizer, sunscreen, face pack, you name it!

Note of Interest: Only people with Skin Types I, II, or III are eligible to participate in the US FDA’s sunscreen testing protocol.

(I) Always burns easily; never tans (sensitive).

(II) Always burns easily; tans minimally (sensitive).

(III) Burns moderately; tans gradually (light brown) (normal).

Thanks for the question 🙂

…I personally reference Skinacea’s UV filters chart and always pick sunscreens with zinc oxide and/or tinosorb. If the Bioderma is too expensive, there are definitely much cheaper Japanese and European sunscreens with great protection out there! Probably same amount of hassle in terms of shipping though

Thanks for writing back 🙂

Tinosorb S, M and Mexoryl SX, XL seem to have pretty similar protection. Though I haven’t looked at the numbers stringently I would say Tinosorbs tend to offer more absorbance (though I don’t have the concentrations)

(It’s not really fair to compare Mexoryl XL with Tinosorb S, it would have been better to compare Mexoryl XL with Tinosorb M as the curves are more similar)

I’m going to see if I can find more graphs with labelled axes for different sunscreens and actually graph them all together 🙂

Problem is, the amount used is still limited by Health Canada – not to mention companies choosing to manufacture with these sunscreens have to pay an additional fee. It’s worse in the US as their use is banned.

I’m pretty happy with the Bioderma’s texture, it’s a bit oily on me because of the dimethicone, and makes me shiny by the end of the day, but it’s a small price to pay.

While I do like the texture of Asian sunscreens, I don’t like the PA++++ system, as you can’t tell the difference between say, a UVAPF 20 and a UVAPF 16, as they’d both be the maximum PA++++.

Unfortunately Health Canada doesn’t require UVAPF testing, so it’s not clear what the actual UVA protection is.

Ombrelle does contain 3 sunscreens with UVA coverage, but Health Canada has limited how much can be used:

Avobenzone 4%

Drometrizole Trisiloxane (Mexoryl® XL) 2.5%

Terephthalylidene Dicamphor Sulfonic Acid (Mexoryl® SX) 0.5%

You do raise a good point though, and it’s better to be sure than to assume. I’ll be switching to a European sunscreen, Bioderma Photoderm MAX SPF 50+ with a tested UVAPF of 42.

Having seen the photodamage on my face now, I think the extra hassle, shipping, and price is worth it.

Especially after you consider that UVA (which UVAPF is a protection factor for) is mainly responsible for increased pigmentation, as well as cell and DNA damage.