How to read an INCI list like a chemist
The ingredients list is not a marketing document. Here is how to actually read it, and what to look for.
Ingredients are listed by concentration, mostly
INCI lists run in descending order of concentration down to about 1 percent. Below 1 percent, ingredients can be listed in any order. That means the first 5 to 8 ingredients tell you the bulk of the formula; the tail is mostly preservatives, actives at their effective low percentages, and fragrance.
Where the actives usually sit
Niacinamide at 5 percent is often in the top 5 ingredients. Salicylic Acid at 2 percent tends to sit in the middle. Retinol at 0.3 percent lives in the last third. Position tells you roughly how much is in there.
The tail matters
Phenoxyethanol, Ethylhexylglycerin: preservatives. Xanthan Gum: texture. Sodium Hydroxide: pH adjuster. None of these are bad; they are the load-bearing structure that keeps a formula stable and safe.
Red flags
Very long fragrance blocks in a product marketed for sensitive skin. Denatured alcohol (Alcohol Denat) in the top 5 of a hydrating serum. Inconsistent claims: a product that says fragrance-free with Parfum listed in the middle of the INCI.