Beauty of Joseon Relief Sun : Rice + Probiotics SPF 50+ PA++++ Versus Skin + Me Daily Moisturiser With SPF 50

Your skin makes glycerin on its own (mostly from sebaceous oil breakdown) and shuttles it to your outermost layer of skin, or your epidermis, via aquaporin-3.

Aquaporin-3 is a transporter that is essential for normal skin hydration, elasticity, and repair. Interestingly, mice lacking in AQP3 have dry and less elastic skin that can be fully corrected with glycerin.

This ingredient is non-irritating, plays well with almost every ingredient, and works across all skin types. Typical use is anywhere between 3-10% but can go up to 79% in some leave-on products.

Just know very high concentrations (>40%) can feel tacky in low humidity.

Glycerin is the name for this ingredient in American English. British English uses Glycerol/Glycerine.

One manufacturer claims this ingredient to have a pH range of 2-8 and to be biodegradable.

This ingredient is also known as Sepimax Zen.

This ingredient is biodegradable and commonly available in natural/COSMOS-certified grades.

On the safety side, it's well-studied and has a solid track record. Human repeat-insult patch testing showed no skin irritation or sensitization even at 100%.

Typical use levels are pretty tiny, usually less than 1%.

You might see some fear-mongering around this ingredient:

Studies in male rats showed kidney effects but that's because of a rat-specific protein that humans don't make. So this study isn't really relevant to humans.

Though it's not a typical fragrance like parfum, it does have a natural scent. That's why the official COSIng database lists it as 'perfuming' ingredient. It can be used to modify the scent of a formula.

Topically applied tocopherol has been shown to protect against UV damage by ramping up the skin's own natural defense enzymes.

It also acts as a skin conditioning agent; some studies show that regular topical use can improve the skin's water-binding capacity over 2-4 weeks.

This ingredient is especially loved for being a team player. When combined with Vitamin C, the photoprotective effect of both ingredients roughly doubles and the combo also helps reduce UV-induced DNA damage.

This ingredient has some brightening potential but it's more of a prevention ingredient than spot-fader. Cell studies show it can slow down melanin production but it's worth noting that it's not the most powerful brightener out there.

In formulations, it also serves as a stabilizer that helps protect other oxidation-prone ingredients from degrading.

Concentrations usually range from 0.1-1% in most leave-on products.

You'll also recognize water as that liquid we all need to stay alive. If you see this, drink a glass of water. Remember to stay hydrated!

Xanthan gum is a pretty common and great ingredient. It is a natural, non-toxic, non-irritating ingredient that is also commonly used in food products.