How do you read a cosmetic ingredient list?

Read it from the top down. Ingredients above 1% are listed in descending order of concentration; at 1% or less they may appear in any order. Names follow INCI, a shared international system, so an ingredient carries the same name across markets. The list gives no percentages, and fragrance allergens above set thresholds are named individually in the EU.

Rule 1: descending order, down to 1%

In the United States (21 CFR 701.3), Canada (Cosmetic Regulations) and the European Union (Regulation 1223/2009, Article 19), ingredients are listed in descending order of their concentration in the product. Below the 1% line, they may be listed in any order.

Two consequences follow. The first few names make up most of the product. And the order of the names near the end tells you only that they are present in small amounts, not which is smallest, unless the brand says it sorts them all.

Most leave-on formulas contain a great deal of water, so "Water" or "Aqua" usually comes first.

Rule 2: INCI names are standard names

INCI stands for International Nomenclature of Cosmetic Ingredients. Each ingredient is given one name, so a list reads the same way in every market that uses the system. Some names are chemical (Sodium PCA), some are trivial names (Glycerin), and plant ingredients follow a set pattern: Latin genus and species, the common name in brackets, then the plant part and the form. For example, Melaleuca Alternifolia (Tea Tree) Leaf Oil.

EU labels list water as "Aqua"; US labels use "Water". Otherwise the same name appears wherever the system is used.

Rule 3: fragrance and allergens

A blend of scent ingredients may be declared under one word, "Fragrance" or "Parfum". In the EU, specific fragrance allergens must also be named individually when they exceed 0.001% in a leave-on product or 0.01% in a rinse-off product. That is why names such as Limonene or Citronellol appear at the end of some lists. More detail: fragrance allergens.

Essential oils and plant extracts can carry scent and allergens of their own even when no "Parfum" appears. If you react to scent, read the whole list, not only for the word fragrance. See patch testing and declared allergens.

Rule 4: no percentages

The law requires identity and order, not amounts. Exact percentages stay with the manufacturer. Where a brand wants to tell you how much of a featured ingredient a product contains, it declares that separately from the ingredient list.

This is why position matters more than prominence. An ingredient named on the front of a pack can sit near the end of the list.

A worked example: Hydrating NanoSerum

The full declaration for the Hydrating NanoSerum sealed vial set, as published:

Water, Glycereth-26, Butylene Glycol, Sodium PCA, 1,2-Hexanediol, Sodium Polystyrene Sulfonate, Betaine, Trehalose, Polyglyceryl-4 Caprate, Ectoin, Stearic Acid, Hydrogenated Lecithin, Nicotinamide Adenine Dinucleotide, Niacinamide, Ethylhexylglycerin, Adenosine, Disodium EDTA, Caprylyl Glycol, Sodium Hyaluronate, Ceramide NP.

Reading it with the four rules:

• The base. Water comes first. Glycereth-26 and Butylene Glycol follow; both are humectants that hold water and give the texture.
• The humectant group. Sodium PCA, Betaine, Trehalose and Ectoin sit high in the list, with Glycereth-26 and Butylene Glycol.
• Formulation helpers. 1,2-Hexanediol, Ethylhexylglycerin and Caprylyl Glycol are multifunctional ingredients commonly used to support a preservation system. Disodium EDTA binds trace metals. Polyglyceryl-4 Caprate, Stearic Acid and Hydrogenated Lecithin help combine water- and oil-loving ingredients.
• The end of the list. In this declaration, the ingredients below 1% are also listed by concentration, so the last names are the smallest amounts. Sodium Hyaluronate and Ceramide NP are present, in the smallest amounts in this formula.
• What is absent. No "Parfum", no essential oil and no other scent-bearing ingredient.

Compare the Clarifying NanoSerum sealed vial set, whose declaration ends with Rosmarinus Officinalis (Rosemary) Leaf Extract and Melaleuca Alternifolia (Tea Tree) Leaf Oil. Tea tree oil is an essential oil, so that formula is not fragrance-free even though "Parfum" does not appear.

Beyond the list

A list is an inventory. Concentration, pH, particle size, manufacturing and performance are documented elsewhere. For how to weigh a claim about results, see what testing claims on a label mean. For what regulators review, see how cosmetics are regulated.

Professional questions on declarations and documentation: professional FAQ. More guides: Beauty Science knowledge.

Sources

• 21 CFR 701.3, Designation of ingredients.
• Cosmetic Regulations, C.R.C., c. 869, section 21.3.
• Regulation (EC) No 1223/2009 on cosmetic products, Article 19(1)(g) and Annex III.
• Personal Care Products Council. International Cosmetic Ingredient Dictionary and Handbook.