Document 6478194

dermatology Barbara Rutledge
In search of lighter skin
An array of skin lightening options exist for those suffering from pigmentation disorders, including
the controversial “gold standard” hydroquinone. Barbara Rutledge PhD reviews the alternatives
S
kin appearance can have a profound psychosocial impact. Although clinically benign, conditions such as
melasma that cause sections of facial skin to become
darker (hyperpigmentation) can be distressing to the affected individual, particularly if the hyperpigmented areas are
perceived as cosmetically unattractive.
Hyperpigmented areas can gradually fade without treatment,
but affected individuals may try to make the darker areas disappear quickly by applying a home remedy, an over-the counter
skin-lightening cream, or a topical medication prescribed by a
dermatologist. In other cases, individuals not suffering from pigmentation disorders may still seek to lighten their skin colour,
with cultural expectations that lighter skin confers social and
economic advantages.
Hyperpigmentation consists of excessive deposition of melanin in the epidermal or dermal layers of the skin. The most common causes of the condition, especially on facial skin, are melasma and post-inflammatory or drug-induced hyperpigmentation.
Melasma is a condition that can affect anyone but around
90% of cases occur in women, particularly those with darker
complexions and usually appears as symmetrical brown patches
on the face. Triggers for melasma include UV radiation, perfume, and oestrogen exposure through oral contraceptives,
pregnancy or hormone replacement therapy.
Post-inflammatory hyperpigmentation can occur following
an outbreak of acne vulgaris, eczema, contact dermatitis or other
inflammatory skin condition, particularly in those with darker
skin. Dr Ophelia Dadzie, a London-based consultant dermatologist and dermatopathologist, says: “Darker pigmented skin
has a tendency to respond to trauma to the skin by healing with
pigmentary abnormalities including hyperpigmentation. This
is obviously distressing for the individual concerned, who may
seek out a skin lightening agent to treat this problem.”
Skin-lightening agents
Most depigmenting agents act by interfering in the pathways
leading to melanin synthesis and/or melanin uptake by keratinocytes. One mechanism is inhibition of tyrosinase, the enzyme
that converts dopa to tyrosine in the melanin synthesis pathway.
Tyrosinase inhibitors are widespread in nature. Botanical
extracts provide a source of naturally occurring tyrosinase inhibitors and some are used in traditional remedies for pigmentation disorders. Bearberry plants produce arbutin, a glycosylated
hydroquinone present in many skin-lightening formulations.
Licorice extract and kojic acid are other common ingredients in
over-the-counter preparations.
Depigmenting agents are routinely used to reduce excessive
pigmentation in melasma and post-inflammatory hyperpigmentation. In their most controversial cosmetic use, depigmenting
agents are active ingredients in skin-bleaching creams or “fairness creams” that are used on normal skin for the purpose of
lightening not just hyperpigmented areas, but the entire skin.
The composition of skin-lightening preparations varies, but
the following ingredients are commonly used.
If dermatologists worldwide were asked to select the most ef-
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fective compound for treating hyperpigmentation
disorders, hydroquinone would top the list as
the “gold standard.” But there would certainly not be universal agreement about
the compound’s safety. As its chemical name—dihydroxybenzene—
indicates, hydroquinone is closely
related to benzene, a known
carcinogen.
The legal status of hydroquinone in cosmetic
treatments varies according
to country. Since 2001, the
EU has classified hydroquinone as an agent that might
cause cancer. The compound
is banned in over-the-counter
cosmetic preparations in the
UK, but is still permitted in
prescription formulations.
By contrast, hydroquinone
is readily available in the US
and many other countries.
Two side effects associated
with hydroquinone use led to its
EU ban: persistent hypopigmentation, known as leukoderma-enconfetti; and exogenous ochronosis, a
condition resulting from melanin deposition in connective tissue of the dermis.
Dr Wiete Westerhof, emeritus associate
professor of dermatology at the University
of Amsterdam and founder of Color Foundation in Landsmeer, says that possible carcinogenic effects of long-term hydroquinone use,
such as aplastic anaemia and acute myeloid leukaemias, need to be investigated.
“Hydroquinone applied to the skin is absorbed by the bloodstream, bypassing
the liver,” he says. Non-metabolised hydroquinone
can reach the bone
marrow, where it
is rapidly oxidised
to the powerful
carcinogen p-benzoquinone. Toxicology studies in
animal models did
not examine the
effects of topical
administration of
hydroquinone.
Tr e t i n oi n ,
which is a retinoid,
body language www.bodylanguage.net
dermatology Barbara Rutledge
Treatments
Laser treatments may be effective in
treating pigmentary disorders, but topical
treatments such as creams and gels are readily available to consumers and are more widely
used. The preparations are usually a combination
of two or more agents. For example, a prescription
medication available outside the EU is Tri-luma
cream from Galderma Laboratories, which contains fluocinolone acetonide 0.01%, hydroquinone
(HQ) 4%, and tretinoin 0.05%.
Over-the-counter treatments for hyperpigmentation may combine plant
extracts containing tyrosinase inhibitors (some
of which are closely
related to hydroquinone), with mild exfoliating agents. The
2001 ban means that
hydroquinone cannot be an ingredient
in over-the-counter
cosmetic preparations
sold legally in the UK.
But some market-
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ing-savvy companies try to turn this restriction to their advantage, emphasising the non-chemical composition of their products. For example, advertisements for Nur76 skin whitening and
skin bleaching cream boast that the cream contains only natural
plant extracts and does not contain hydroquinone. While truthful, the claim is disingenuous. One of the Nur76 ingredients
listed is bearberry extract which contains arbutin, which is also
listed separately as an ingredient. Arbutin is a glycosylated form
of hydroquinone.
Despite the ban, it is not difficult to obtain skin-bleaching
products containing hydroquinone in the UK. “A trip to any
beauty shop or market in an area populated by ethnic minorities will demonstrate the availability of such products,” says Dr
Dadzie. “Active ingredients include hydroquinone and its derivatives, high-potency steroids and even mercurials.” The concentrations in counterfeit products or illegal formulations may
also be much higher than indicated on the label.
The greatest health risk from skin-lightening preparations is
not to melasma sufferers, but to those who practice skin bleaching to lighten the pigmentation of their entire body. Prescription
skin-lightening creams containing hydroquinone are intended
for intermittent use and application to a relatively small area of
skin. By contrast, skin bleaching may involve multiple daily applications of a skin-lightening cream over the entire body and
the practice can continue for decades. “I often find that people
do not confess to this practice,” says Dr Dadzie. “It only becomes apparent when they present with a problem associated
with the abuse of depigmenting agents.” Patients have described
skin bleaching as an addiction—they feel unable to stop for fear
that their skin will become even darker than normal.
Individuals prone to melasma or post-inflammatory hyperpigmentation are advised to protect their skin from direct sun
exposure and to use a broad-spectrum sunscreen with an SPF
rating of 30 or above. Rather than self-treat pigmentation disorders with home remedies or over-the-counter preparations, it’s
best to consult a dermatologist. Dermatologists can prescribe
safe treatments without hydroquinone or its deratives. Dr Westerhof reports successful treatment of melasma using an ointment
containg 2% N-acetyl-cysteine, 2% ascorbyl palmitate (a vitamin C derivative), and 5% Į-tocoferol (vitamin E).
Dr Dadzie recommends that patients refrain from using cosmetic preparations to lighten their normal skin colour. “They
need to explore their motivation for wanting this and address
issues about their self esteem, perhaps with the help of a psychologist,” she says. Dr Westerhof acknowledges the cultural
pressures favouring lighter skin that darker-skinned individuals face, and he insists that society has to change. “The government has to fight discrimination based on skin colour,” he says.
“Color Foundation (http://www.colorfoundation.org) is active
in bringing attention and support for this cause.”
Barbara J Rutledge PhD is a freelance journalist
DR DADZIE
or vitamin A derivative, is marketed for the treatment of acne
vulgaris and for fine wrinkles. Tretinoin accelerates the turnover of epidermal cells and causes shedding of the outer layer of
skin. Side effects associated with topical application of retinoin
include redness, swelling, dryness, itching and blistering. Postinflammatory hyperpigmentation can also occur, particularly in
darker skin.
Azelaic acid, a naturally occurring dicarboxylic acid, is
used for the treatment of acne. Azelaic acid is a tyrosinase inhibitor that may also have a cytotoxic effect on melanosomes. Side effects of azelaic
acid are similar to those of tretinoin.
Corticosteroids lighten skin by affecting melanin synthesis, although
the mechanism of action is not well
understood. Corticosteroids also
alleviate the skin irritation caused
by other ingredients in depigmenting preparations, such as hydroquinone and tretinoin. Use of topical
corticosteroids can lead to serious
side effects, including suppression
of the hypothalamic-pituitary-adrenal axis. Highly potent corticosteroids such as clobetasol propionate should be used only under the
supervision of a dermatologist.
Alpha hydroxy acids cause
shedding of the epidermal layer
of the skin. The most common
alpha hydroxy acids used in
cosmetic products are glycolic
acid, lactic acid, and citric acid.
Salicylic acid, or beta hydroxy
acid, is a closely related compound
similarly used in chemical peels and
resurfacing treatments.
Patient with stretch marks from excessive use of a skin lightening cream
containing steroids
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