Niacinamide, beneficial effects for dry skin?

It is said that a person suffers from dry skin when the sebum production is less than 0.5 mg/10 cm2 every three hours, whereas the average rate in an adult is 1 mg/10 cm2.

Dry skin is skin that does not contain enough moisture to remain supple and soft to the touch. In addition to a decrease in sebum production by the sebaceous glands, dry skin is also linked to changes in the lipid components of the stratum corneum, particularly marked reductions in ceramide levels, giving the skin this characteristic rough texture that can itch, peel or appear scaly. However, reports have suggested that the topical use of nicotinamide could have beneficial effects on skin dryness.

• An in vivo study assessed the effects of twice-daily topical application of 2% niacinamide in a 0.1% solution of polyoxyethylene sorbitan monolaurate on the dry skin of 12 healthy human volunteers. After 4 weeks of application, a decrease in transepidermal water loss was observed on the skin treated with niacinamide, 27% lower than that of the skin treated with the excipient (without niacinamide), which resulted in an improvement of the impaired epidermal barrier .

• In a comparative study, the effect of topical nicotinamide on atopic dry skin was compared to that of vaseline, which served as a control, by specifically measuring the normal passive water loss through the skin (TEWL) and the hydration of the stratum corneum.

  28 patients suffering from atopic dermatitis, who exhibited dry skin lesions on both forearms, were recruited and instructed to apply a cream containing 2% niacinamide to the left forearm twice daily, and vaseline to the right forearm, for a period of 4 or 8 weeks.

  The results demonstrate that niacinamide has significant hydrating effects on atopic dry skin. It has been found to reduce transepidermal water loss, which consequently led to an increase in water content in the stratum corneum and accelerated the restoration of the skin barrier. Furthermore, the niacinamide cream proved to be more effective than petroleum jelly.

• In another left-right comparative study from 2013, the forearms of 20 healthy volunteers (25 cm2) were subjected to the application of a moisturising cream containing 5% nicotinamide along with commonly used excipients in topical formulations (propylene glycol, miglyol and propylene glycol monolaurate) or a moisturising solution without niacinamide as a reference (2mg/cm2), twice daily for 28 days. After this period, the sites treated with niacinamide showed a reduction in water loss through the skin compared to the baseline before treatment and the untreated control.

Even though the results are clinically significant and the data suggests a real benefit of niacinamide on dry skin, the obtained results must be interpreted with caution. Indeed, the studies present some limitations that require further investigations (small sample size, non-exclusive formulation, etc.).

By what molecular mechanisms?

Based on the results obtained, the topical application of niacinamide improved the condition of the skin's natural hydration barrier through a number of biophysical and molecular mechanisms. It would increase the rate of biosynthesis of ceramides, cholesterol, free fatty acids, as well as other fractions of epidermal sphingolipids (glucosylceramide and sphingomyelin) in the stratum corneum in a dose-dependent manner. Indeed, these lipid compounds play a central role in the structural and functional integrity of the barrier function of the stratum corneum

Nicotinamide would actually act and regulate the activity of a key enzyme in the synthesis of sphingolipids, called serine palmitoyltransferase, to induce these actions. By strengthening the intercellular lipid bilayer, niacinamide would thus help to prevent water loss and maintain optimal hydration levels in the skin, making it particularly beneficial for dry skin.

Furthermore, in a 2001 study, SCHNICKER M. S. and his colleagues cultivated normal human epidermal keratinocytes, which are cells that make up about 90% of the skin's superficial layer, until they were almost confluent, and then supplemented the medium with niacinamide. After 24 hours of incubation, the results initially showed a rise in the number of keratinocytes treated with niacinamide compared to the control vehicle.

Secondly, epidermal cells incubated with niacinamide demonstrated a heightened increase in the biosynthesis of epidermal intermediates essential for the formation of a functional stratum corneum, involucrin and filaggrin, compared to that induced by a control vehicle. It has been suggested that this could be due to a rise in intracellular levels of the reduced forms of nicotinamide (NADH) initiated by topical niacinamide. This positive natural barrier effect was thus accompanied by a boost in the renewal rate of the stratum corneum.

To enhance the moisturising capacity of the treatment and lead to improved effectiveness in maintaining hydrated, supple and soft skin, the niacinamide can be combined with other hydrating agents (hyaluronic acid, glycerine, sodium PCA, etc.), while providing relief to dry and tight skin.