Vitamin F is a legacy European skincare term, not a true vitamin by modern definition, referring to the essential polyunsaturated fatty acids linoleic acid and alpha linolenic acid, which the body cannot make on its own. Linoleic acid is a critical structural component of the ceramides that make up the stratum corneum's intercellular lipid matrix, and a genuine essential fatty acid deficiency is directly linked to a defective barrier and increased water loss.
Alpha linolenic acid contributes anti inflammatory activity by modulating prostaglandin pathways. The most rigorous evidence for this barrier role comes from essential fatty acid deficiency and tissue engineered skin models rather than large randomized human trials on finished products labeled vitamin F, and since the term is not regulated, actual fatty acid ratios vary widely between products.
Vitamin F References
Alpha linolenic acid and linoleic acid modulate the lipidome and the skin barrier of a tissue engineered skin model, 2021
The Permeability Barrier in Essential Fatty Acid Deficiency, Evidence for a Direct Role for Linoleic Acid in Barrier Function, Journal of Investigative Dermatology
Our team reviews ingredient research and uses up-to-date evidence to rate ingredients based on the categories below.
Best
Ingredients with the most rigorous and convincing evidence. These are the standouts backed by consistent findings across independent, peer reviewed clinical research.. When we call an ingredient Best, it has earned that distinction through genuine, reproducible proof that it improves skin.
Good
Reliable, well tolerated ingredients that do their job without complaint. They may not carry the headline benefits of a Best rated active, but they hydrate, stabilize a formula, or support the ingredients around them in ways that make a real difference in how a product performs and feels.
Average
Ingredients that are perfectly safe and serve a clear function, typically as an emollient, thickener, or filler, but do not offer any meaningful skin benefit beyond that basic job. Not a red flag, just not a reason to choose one product over another.
Bad/Worst
Ingredients with documented potential to irritate skin, disrupt the barrier, or trigger sensitization in some users, often synthetic fragrance, drying forms of alcohol, or certain essential oils. Not automatically a dealbreaker for every skin type, but worth knowing about before you commit to a product.
