Is It Better to Take Linoleic Acid as a Supplement or Apply It Topically for Hair Growth?

Linoleic acid (LA) is an omega-6 polyunsaturated fatty acid. The body cannot make it, so it comes from food (for example sunflower, safflower and soybean oils, nuts and seeds) or from products applied to the skin. It is part of the skin's lipid barrier, which is why it appears in both supplements and scalp oils.

No study has compared the two routes

No published trial has compared oral linoleic acid with topical linoleic acid for hair growth. Any claim that one route is "better" goes beyond the evidence.

What is known about oral use

The only human hair study we found that involves oral omega-6 fatty acids is a 6-month randomized comparative trial in 120 women (Le Floc'h et al., 2015). Women who took a supplement containing omega-3 and omega-6 fatty acids plus antioxidants had less telogen (resting-phase) shedding and better photo scores than the untreated control group. The product mixed several ingredients and was not compared with a placebo, so the result cannot be attributed to linoleic acid.

Linoleic acid deficiency is rare in people who eat a normal diet. There is no evidence that taking extra linoleic acid improves hair in people who are not deficient.

What is known about topical use

• Cell studies: in cultured human dermal papilla cells, linoleic acid raised growth-factor signals and lowered DKK-1, a signal linked to androgen-related hair loss (Ryu et al., 2021). This was a laboratory experiment, not a test on people.
• Skin penetration: a laboratory study on human scalp skin found that linoleic acid from a 1% formulation collected mainly along the hair sheath, suggesting it can travel down the follicle (Raufast & Mavon, 2006).
• Reviews: a 2024 review describes hair-growth effects of linoleic acid or linoleic-acid-rich oils in animal and skin-cell models, and says more clinical studies are needed (Wang, Jia & He, 2024).

No controlled human trial has tested topical linoleic acid on hair density or hair loss.

Practical points

• Linoleic acid oxidizes easily. Old or poorly stored oils can irritate the scalp.
• Stop using a product that stings, itches or reddens the scalp.
• Treatments for pattern hair loss that have been tested in controlled trials are a separate discussion; talk to a doctor or pharmacist before starting or changing a treatment.

References

Le Floc'h, C., Cheniti, A., Connétable, S., Piccardi, N., et al. (2015). Effect of a nutritional supplement on hair loss in women. Journal of Cosmetic Dermatology, 14(1), 76–82. https://pubmed.ncbi.nlm.nih.gov/25573272/

Ryu, H. S., Jeong, J., Lee, C. M., Lee, K. S., et al. (2021). Activation of hair cell growth factors by linoleic acid in Malva verticillata seed. Molecules, 26(8), 2117. https://pubmed.ncbi.nlm.nih.gov/33917070/

Raufast, V., & Mavon, A. (2006). Transfollicular delivery of linoleic acid in human scalp skin: permeation study and microautoradiographic analysis. International Journal of Cosmetic Science. https://pubmed.ncbi.nlm.nih.gov/18492146/

Wang, X., Jia, Y., & He, H. (2024). The role of linoleic acid in skin and hair health: A review. International Journal of Molecular Sciences, 26(1), 246. https://pubmed.ncbi.nlm.nih.gov/39796110/