The second class of skin lightening agents is the one of the non-phenolic compounds. Equally to the phenolic compounds of which we already discussed, these agents are used to treat melasma and post-inflammatory hyperpigmentation.
Aloe Vera Extract
Aloin is extracted from the leaves of Aloe Vera which is a common ingredient in many cosmeceutical formulations. One in vitro study on animal cells showed skin lightening potential.1
Glabridin is a poyphenolic flavonoid and the main component of licorice extract. In one in vitro study on animal cells, it showed anti-inflamatory properties and protective effect against UVB induced pigmentation. It also showed inhibition of melanin biosynthesis and dispersion of melanin with improvement of hyperpigmentation.2
Chemically speaking, soy is made up of many different types of molecules, from phospholipids to vitamins to inhibiting enzymes. For this reason it influences the pigmentation’s biological pathway in multiple ways and has been proven effective in improving skin tone and general appearance counteracting photo damage. Soy extract effects are visible since week 2 of daily application and its use is considered safe.3
Kojic acid is a bioproduct derived from some fungal species. It is a potent antioxidant and effective in improving pigmentation disorders by inhibiting the enzyme responsible for melanin production. It is usually found in formulations containing hydroquinone and glycolic acid too. Its most reported side effect is contact dermatitis, especially in Japan where it is widely used.
Azelaic acid is the bioproduct of the fungal genus Pityrosporum ovale; it is used in combination with other agents or alone in 10-20% concentrations. It appears to not be effective against normal melanocytes and pigmented skin; however, it shows anti-proliferative and cytotoxic effect on abnormal melanocytes and interferes with tyrosinase activity. While usually well tolerated, it might cause transient erythema and scaling, but the side effects are usually mild and subside within 2 to 4 weeks.
Retinoids are the derivates of vitamin A. Tretinoin, also known as retinoic acid, is used in topical formulation and combination therapies in 0,025-0,1% concentrations and the first use to improve skin tone dates back to 1975. It decreases hyperpigmentation through multiple mechanisms. Retinoids need long term daily application and their effect becomes evident after 24 weeks of treatment. Erythema and scaling are possible side effects: when using retinoids it is fundamental and mandatory to use sunscreens to prevent sunburns and additional photo-damage.
Niacinamide, the physiologically active form of vitamin B3, has been proven effective at preventing the transfer of melanin from the melanocytes to the keratinocytes. Clinical trials report efficacy following a 4 week treatment using 2% concentration. Moreover, studies also showed how daily use of niacinamide with sunscreen reduced the hyperpigmentation and increased the lightness of the basal skin, when compared to the use of sunscreen alone.
Ascorbic acid, or vitamin C, interferes with melanin production through multiple modalities. It is unstable and has low skin penetration potential, so it needs to be used in formulations where these issues have been overcome. Given the lack of significant side effects, it is widely used in cosmetic formulations and in combination therapies against hyperpigmentation.
Warning and Advices
- Although being there many more active ingredients currently marketed as skin lightening agents, there are limited or no studies both to support efficacy and to understand their safety profile. Always ask your physician or dermatologist for a consult before trying a new product.
- Some of the side effects caused by these topical formulations are skin irritation, redness, dryness, scaling, pruritus, burning sensation and contact dermatitis. To test your reaction to a product before using it on large areas you might want to do a patch test by applying a small quantity of cream to a limited area, such as a spot on the inside of your arm, and wait 24h before assessing if any reaction occurred.
- Always apply products to clean and dry skin, nighttime is usually the best.
- There are several combination therapies available which are those leading to the best results against hyperpigmentation due to combining different mechanism of actions and interferences in melanin production and storage. Ask your trusted physician for an advice, in order to establish and assess the best therapeutic approach tailored to your needs and conditions.
- Daily use of broad-spectrum sunscreens is mandatory to achieve results in treating conditions such as melasma.
Last edit: 25/05/2018
1. On the novel action of melanolysis by a leaf extract of Aloe vera and its active ingredient aloin, potent skin depigmenting agents. Ali SA, Galgut JM, Choudhary RK Planta Med. 2012 May;78(8):767-71. https://www.ncbi.nlm.nih.gov/pubmed/22495441/ 2. The inhibitory effect of glabridin from licorice extracts on melanogenesis and inflammation. Yokota T, Nishio H, Kubota Y, Mizoguchi M. Pigment Cell Res. 1998 Dec;11(6):355-61. https://www.ncbi.nlm.nih.gov/pubmed/9870547/ 3. Efficacy of a soy moisturizer in photoaging: a double-blind, vehicle-controlled, 12-week study. Wallo W, Nebus J, Leyden JJ. J Drugs Dermatol. 2007 Sep;6(9):917-22. https://www.ncbi.nlm.nih.gov/pubmed/17941363/ 4. Cosmeceuticals for Hyperpigmentation: What is Available? Rashmi Sarkar, Pooja Arora, and K Vijay Garg J Cutan Aesthet Surg. 2013 Jan-Mar; 6(1): 4–11. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3663177/