Propylene Glycol is an odorless, colorless liquid. As a humectant, it helps skin retain moisture. It also aids in delivering active ingredients.

Another role of this ingredient is preventing a product from melting or freezing. Propylene glycol also adds antimicrobrial properties to a product, elongating product lifespan.

Salicylic Acid (also known as beta hydroxy acid or BHA) is a well-known ingredient for treating skin that struggles with acne and clogged pores. It exfoliates both the skin's surface and deep within the pores to help clear out buildup, control oil, and reduce inflammation.

Unlike AHAs (alpha hydroxy acids), salicylic acid is oil-soluble. This allows it to penetrate into pores which makes it especially effective for treating blackheads and preventing future breakouts.

Sodium Benzoate is a preservative. It's used in both cosmetic and food products to inhibit the growth of mold and bacteria. It is typically produced synthetically.

Both the US FDA and EU Health Committee have approved the use of sodium benzoate. In the US, levels of 0.1% (of the total product) are allowed.

Sodium Hydroxide is also known as lye or caustic soda. It is used to adjust the pH of products; many ingredients require a specific pH to be effective.

In small amounts, sodium hydroxide is considered safe to use. However, large amounts may cause chemical burns due to its high alkaline.

Water. It's the most common cosmetic ingredient of all. You'll usually see it at the top of ingredient lists, meaning that it makes up the largest part of the product.

So why is it so popular? Water most often acts as a solvent - this means that it helps dissolve other ingredients into the formulation.

Zinc Pyrithione is a preservative. It inhibits the multiplying of fungal and bacterial cells.

You'll most likely find this ingredient in Malassezia treatments. In the US, this ingredient is most common in anti-dandruff shampoos. However, the European Union has prohibited the use of this ingredient starting in 2022.