The 20 most common skincare ingredients, explained in one line

Ingredient lists look long and foreign, but the same twenty names do most of the work across the whole shelf. We counted every ingredient in the 14,065 products we have checked. Here are the twenty that appear most often, with the number of products each one is in and a plain explanation of what it does. If you learn these, you can read most labels.

1. Aqua, 10,154 products

Water. The base of nearly every cream, cleanser, lotion and toner. US labels write Water; EU labels write Aqua. Products without it are oils, balms, sticks and powders.

2. Parfum, 8,177 products

The perfume blend. One word that can stand for dozens of scent molecules, which brands do not have to name except for the EU's listed allergens. Also written Fragrance. The single most common reason a product fails our fragrance free check.

3. Glycerin, 7,589 products

A humectant that draws water into the upper skin and keeps products from drying out. It can be made from plants, from animal fat or synthetically, and the label does not say which. That is why it is the most common cause of a not sure on our vegan check.

4. Citric Acid, 5,269 products

A fruit acid used in small amounts to bring a product's pH down to where the skin and the preservatives want it. Made by fermentation. Not an exfoliant at these levels.

5. Limonene, 4,301 products

A citrus-scented fragrance component that EU labels must name once it passes a small threshold, because it is a recognized contact allergen. Its presence means the product contains fragrance, even if the word Parfum is missing.

6. Sodium Benzoate, 4,281 products

A mild preservative, the most common one in our data, usually paired with potassium sorbate. Works in acidic products, which is why it appears with citric acid so often.

7. Linalool, 4,176 products

A floral, lavender-like fragrance allergen, named on EU labels for the same reason as limonene. Found in lavender, coriander and many essential oils, and also made synthetically.

8. Sodium Chloride, 3,746 products

Table salt. In shampoos and shower gels it thickens the liquid by interacting with the surfactants. Harmless and cheap.

9. Phenoxyethanol, 3,066 products

The preservative that replaced parabens in most leave-on products. The EU caps it at 1 percent. Usually paired with ethylhexylglycerin.

10. Sodium Hydroxide, 2,931 products

Lye, used in tiny amounts to raise pH or to neutralize an acid. In bar soap it is the ingredient that turns oils into soap, and none is left in the finished bar.

11. Cocamidopropyl Betaine, 2,743 products

A mild coconut-derived cleanser that boosts foam and softens sulfates. The backbone of most sulfate free washes. Not a sulfate.

12. Tocopherol, 2,475 products

Vitamin E. Added mostly as an antioxidant to protect the oils in a product from going rancid, and as a skin conditioner. Usually plant-derived from soybean or sunflower oil.

13. Benzyl Alcohol, 2,390 products

A preservative and solvent allowed up to 1 percent, which also sits on the EU fragrance allergen list because it occurs in perfumes. Our checks treat it as a preservative unless the label ties it to the fragrance.

14. Sodium Laureth Sulfate, 2,289 products

The most common sulfate. A strong, high-foam cleanser in shampoos and shower gels. The reason a product fails our sulfate free check far more often than any other ingredient.

15. Propylene Glycol, 2,180 products

A humectant and solvent that helps dissolve other ingredients and keeps products from freezing or drying. Synthetic. Not the same as ethylene glycol, the antifreeze it is often confused with.

16. Potassium Sorbate, 2,173 products

The partner preservative to sodium benzoate. Covers yeasts and moulds where benzoate covers bacteria. Also used in food.

17. Citronellol, 2,117 products

A rose-scented fragrance allergen on the EU list. Common in anything described as rose, geranium or floral.

18. Xanthan Gum, 2,093 products

A thickener made by fermenting sugar. Gives gels their texture and keeps creams from separating. Vegan.

19. Geraniol, 1,905 products

Another rose-like fragrance allergen on the EU list, usually appearing next to citronellol.

20. Hexyl Cinnamal, 1,864 products

A jasmine-like fragrance allergen, also on the EU list. Almost always synthetic.

Just behind the top twenty sit cetearyl alcohol (1,832, a waxy emulsifier that is not a drying alcohol) and dimethicone (1,821, the most common silicone).

What the list tells you

Six of the twenty are fragrance components. Four are preservatives. Only two are cleansers and only two are actives in any meaningful sense (glycerin and tocopherol). The rest are structure: water, salt, pH adjusters, thickeners. That is what a cosmetic is, most of the time: water held in shape, kept from spoiling, and scented.

It also tells you where the checks bite. Fragrance components dominate the list, which is why fragrance free is the hardest of our six checks to pass. Sulfates are on it once. Parabens and silicones are not on it at all, which is why paraben free and silicone free are easy claims to make.

FAQ

Are these ingredients safe?

All twenty are permitted in the EU, and most have been in use for decades. The two groups that cause reactions in some people are the fragrance components and, less often, the preservatives; the allergen labelling rule exists for exactly that reason.

Why is Parfum so high on the list?

Because most products are scented, and the word covers every blend. Parfum alone is in 58 percent of the products we checked.

Which of these are vegan?

All except glycerin are plant, mineral or synthetic and pass a vegan check. Glycerin can be either, which is why the label alone often cannot settle it.

Where can I look up an ingredient not on this list?

Every ingredient in our data has its own page. Start at the ingredient dictionary.