What are the benefits of nettle extract on hair?

Nettles contain polyphenols, compounds with antioxidant properties. These molecules can neutralise free radicals by donating an electron before they weaken the hair bulb and hair fibres, thus promoting the appearance of split ends. Therefore, applying nettle to the hair has a protective effect on the hair and limits the effects of exposure to UV radiation and pollution, elements that generate oxidative stress.

Furthermore, it can be assumed that the antioxidant properties of thenettle allow it to slow down the greying process, or the whitening of hair, which a study has shown to be correlated with the presence of free radicals. Indeed, although the mechanism by which these operate at the level of hair fibres remains poorly understood, it would seem that free radicals could trigger a chain reaction leading to the degradation of melanin, the pigment that gives hair its colour.

Please note : these are indirect evidences, no study has demonstrated that nettle itself prevents the occurrence of split ends and white hair.

Nettle extract acts on scalp inflammations by soothing irritations and reducing itching sensations. Its anti-inflammatory properties operate at various levels within cells. Notably, nettle is capable of inhibiting 5-lipoxygenase, an enzyme that plays a key role in the metabolism of arachidonic acid. This acid, in turn, stimulates the activity of cyclooxygenases COX-1 and COX-2, molecules that catalyse the formation of prostaglandins, which are inflammatory mediators.

It has also been demonstrated that nettle inhibits the NF-κB pathway, which is involved in immune and inflammatory responses. Studies in vitro have also proven that this ingredient downregulates the release of interleukins IL-2 and IL-1β and the tumour necrosis factor TNF-α. These are pro-inflammatory cytokines, which are also involved in irritations and itching.

Affecting one in two people, dandruff is a common hair disorder. Several factors have been identified as contributing to the onset of dandruff, among which is an overgrowth of Malassezia type fungi. By hydrolysing the triglycerides present in sebum, these pathogens are responsible for the production of pro-inflammatory mediators. In addition to helping fight inflammation, nettle extract has an antifungal activity against these fungi, which is attributed to the polyphenols it contains.

A study has particularly focused on the anti-dandruff effects of nettle. Over a period of five weeks, three times a week, 60 individuals with dandruff applied a shampoo containing piroctone, climbazole, and extracts of nettle, chamomile, rosemary, sage, peppermint, and wheat germ. At the end of the five weeks, the researchers observed that 80% of the participants no longer had dandruff and that 20% had significantly less. Although the shampoo contains several active ingredients, the scientists attribute a large part of its effectiveness to the nettle extract.

Studies have also highlighted that nettle can help to reduce hair loss. In one such study, 120 individuals suffering from androgenetic alopecia and telogen effluvium applied a shampoo and serum containing nettle extract for six months. At the end of the six months, researchers noted a 90% reduction in their hair loss, compared to a 40% decrease in participants who received placebo treatments.

This property of nettle is explained once again by its inhibitory action on 5-α-reductase, the enzyme responsible for the conversion of testosterone into dihydrotestosterone (DHT). Indeed, DHT intensifies the activity of interleukin-6 (IL-6), cytokines that accelerate the transition between the growth and rest phases of hair. DHT thus more rapidly induces hair follicles into the telogen phase, or hair shedding phase. By inhibiting 5-α-reductase, nettle thus protects the hair from hormonal variations or genetic predispositions leading to an increased production of DHT and consequently to hair loss.