Once upon a time in Western culture, being tanned was a sign of wealth—tanned skin indicated that instead of slaving away in an office, one had all the time and money to enjoy the world’s most beautiful beaches. At another point in time, being tanned was a sign of poverty, indicating that you labored for a living.
Today, we strive for the middle. More aware of the dangers of unprotected sun exposure, consumers understand the value of sunscreen, and strive for a complexion that is fair, even but still shows a bit of sun.
Understanding the way melanin works is key to creating products that help one achieve this perfect complexion. In this review, we look at both the causes of heavy pigmentation and at some of the ingredients that aim to even out pigmentation and improve the evenness of complexion.
Cause of Pigmentation
Pigmentation is a complex metabolic process that includes tyrosinase activity, melanosome formation and a cascade of intermediate metabolites that result in the formation of melanin.
Melanin is both good and bad. The most important positive role of melanin is protecting the skin against UV radiation. Melanocytes are, therefore, important for the human body. However, when melanogenesis becomes hyperactive in melanocytes, the skin develops epidermal hyperpigmentation—including melasma, freckles and senile lentigines. In lay terms, melanin hyperactivity can lead to unsightly brown spots.
Let’s look more specifically at the three main causes of hyperactive melanin.
Ultraviolet radiation directly stimulates melanin synthesis and the proliferation of melanocytes, as well as the release of cytokines such as the alpha-melanocyte-stimulating hormones (MSH) from keratinocytes or melanocytes which up-regulate the tyrosinase level in melanocytes.1
Hormones, specifically estrogen, is also involved in the synthesis of melanin. These are hyper-secreted during pregnancy. Melasma (also known as the pregnancy mask) appears at any time during a woman’s reproductive years, and is often associated with pregnancy or oral contraceptive use. It is highly exacerbated by exposure to UV.
Various skin conditions—such as acne, eczema and allergic responses—can lead to post-inflammatory hyperpigmentation. This is an acquired excess of melanin pigments following cutaneous inflammation or injury such as acne, contact dermatitis, atopic dermatitis or trauma. Darkly pigmented individuals are particularly prone to developing this form of hypermelanosis.2
The treatment of pigmentary disorders remains a challenge, as there are no standardized treatments for melasma, post-inflammatory hyperpigmentation or pigmentation due to photoaging. Typically, the use of dual-or triple combination product as a first approach is recommended. The combination of various pharmacologic agents with chemical peels, microdermabrasion, and/or pigment-specific lasers can lead to accelerated healing times and a more rapid and more significant improvement, and can reduce the occurrence of post-inflammatory hyperpigmentation.
The ideal depigmentating compound should have a potent, rapid and selective bleaching effect on hyperactivated melanocytes; carry no short- or long-term side effects; and lead to a permanent removal of undesired pigment, acting at one or more steps of the pigmentation process.
Hydroquinone: What is it?
It is a hydroxyphenolic chemical that inhibits tyrosinase by preventing the conversion of tyrosine to dihydroxyphenylalanine, a precursor of melanin. Hydroquinone may interfere with pigmentation even through alteration of melanosome formation and melanization ectent and selectively damaging melanosomes and melanocytes.
In the U.S., hydroquinone is readily available in concentrations up to 2% as an over-the-counter (OTC) drug and by prescription at higher concentrations.3 It is considered the gold standard for treatment of hyperpigmentation, and has been for over 50 years.
The side effects of hydroquinone include allergic contact dermatitis, irritant contact dermatitis, and post-inflammatory hyperpigmentation and nail discoloration. Irritation, stinging and/or burning have been observed transiently during the first day of application and disappeared with use of the medication after a few days. For these reasons, hydroquinone is banned in the European Union for cosmetic use (prescription only).
Kojic acid: What is it?
Kogic acid is a naturally occurring hydrophilic fungal product derived from certain species of Acetobacter, Aspergillus and Penicillium.
Kogic acid reduces hyperpigmentation by inhibiting the production of tyrosinase and is also a potent antioxidant.4
Kojic acid has the potential to cause contact dermatitis and erythema.5
Arbutin: What is it?
Arbutin is a derivative of hydroquinone, and exists in the dried leaves of certain plant species such as bearberry or blueberry.
Arbutin inhibits tyrosinase activity, inhibits melanosome maturation and is less toxic to melanocytes than hydroquinone. Arbutin is a safe and mild agent for treating cutaneous hyperpigmentation disorders, including melasma and UV-induced hyperpigmentation.
Ellagic acid: What is it?
Ellagic acid is a naturally polyphenol found in plants such as strawberries, grapes and green tea.
Ellagic acid can prevent pigmentation such freckles caused by sun exposure.
Paper mulberry extract: What is it?
Paper mulberry extract comes from the root bark of the Morus alba tree, and has been shown to have a skin whitening properties.
Mulberry leaves have been shown to inhibit tyrosinase activity and melanin formation. No toxicity has been associated with this ingredient, as is shown by many human skin irritation test.
Niacinamide: What is it?
Niacinamide is a biologically active form of vitamin B3 found in many root vegetables and yeasts.
Niacinamide inhibits the transfer of melanosomes from melanocytes to keratinocytes. Furthermore, topical niacinamide has also been shown to decrease collagen oxidation products and improve aging-induced yellowing or sallowness.
Ascorbic acid (vitamin C): What is it?
Vitamin C is an antioxidant that can scavenge free radicals such as peroxides, which contribute to tyrosinase activation and melanin formation.
Topical application of vitamins C decreases the tanning response by inhibiting the UV-induced melanogenesis and proliferation of melanocytes. Cons>>
While vitamin C can momentarily retard the melanin-biosynthesis pathway, it can not eliminate it.
There are three main causes of uneven pigmentation: excessive sun exposure, hormones and trauma that leads to inflammatory hyperpigmentation. Identifying the cause of “brown spots” is key to optimal treatment. Combining therapies with topical products will ensure optimal therapeutic results. And topical products with a combination of ingredients such as those mentioned herein is key.
- G Imokawa et al, Endothelins secreted from human keratinocytes are intrinsic mitogens for human melanocytes. J Biol Chem 267; 24675-24680 1992
- M Chong, Disorders of hyperpigmentation. In: Bolognia J, Jorizzo R, Rapini P, editors. Dermatology : Mosby ; 2008, p939-40 and Rivera AE. Acne scarring: a review and current treatment modalities, J Am Acad Dermatol. 2008; 59(4):659-76
- PG Engasser et al. Cosmetics and dermatology: bleaching creams 1981; Grimes PE Melasma. Etiologic and therapeutic consideration 1995
- V Kahn, Effect of kojic acid on the oxidation of DL-DOPA, norepinephrine, and dopamine by mushroom tyrosinase. Pigment Cell Res. 1995; 8:234-40)
- M Nakagawa et al, Contact allergy to kojic acid in skin care products, Contact Dermatitis 1995