The toxic chemistry behind skin bleaching products

The skin is the body’s largest organ, and humans have evolved to acquire skin colour as a balance between UV protection and vitamin D synthesis. The anatomy of colour remains a relatively under-researched area of medicine, but what is known is there is a strong desire to lighten skin tone in certain communities. Skin bleaching refers to the intentional whitening of someone’s skin colour for cosmetic purposes using products such as soaps, creams and washes – and in some cases, through injections. While evening out skin tone under strict medical guidance happens, the misuse of chemicals in a highly unregulated market is driving an epidemic in some countries. This essentially alters the biochemistry of the skin.

The use of products containing harmful chemicals is on the rise, and with the global skin-lightening market valued at around $10.22 billion in 2025 (£7.5 billion) and projected to exceed $16 billion by 2032, the industry is only thriving. These chemicals have been linked to severe health conditions such as neurological damage and kidney problems, creating a major public-health concern. This demonstrates why scientists, policymakers and the public must unite to stop this harmful practice. Cultural norms, regulatory gaps and industry ethics all contribute to the problem – and beyond biology, this is colonial colourism rendered in chemical form.

How melanin is produced

‘Your skin colour is naturally preset to be a certain colour,’ says Roopal Kundu, a dermatologist at Northwestern University in Illionois, US. Skin colour comes from melanin – the pigment that gives skin, hair and eyes their colours. The enzyme tyrosinase acts as the molecular on-switch for pigment production. Melanin synthesis begins with the amino acid tyrosine, which is converted into DOPA (3,4-dihydroxyphenylalanine) and then into DOPAquinone by the copper-containing enzyme tyrosinase, explains Bianca Tod, a dermatologist in Cape Town, South Africa. These reactions take place inside specialised cells called melanocytes, found in the basal layer of the epidermis – the layer that constantly sheds and renews itself.

From there, DOPAquinone follows one of two pathways, producing either eumelanin (a dark brown to black pigment) or pheomelanin (red to yellow). These pigments are packaged into tiny organelles called melanosomes, which are transported through dendrites into surrounding keratinocytes, the main cells that make up the epidermis. As keratinocytes mature, they carry those melanin granules upwards towards the skin’s surface, where the colour becomes visible.

‘For every one melanocyte, it’s feeding into multiple other keratinocytes,’ says Kundu, describing how a single pigment cell supplies colour to many surface cells – what she calls a ‘melanin unit.’

Melanin is a like a hat protecting the cell’s nucleus from UV

The visible pigmentation of the skin – this intricate melanin unit – depends on the balance between eumelanin and pheomelanin, and on the number, size and distribution of melanosomes. Darker skin produces more melanin, predominantly eumelanin, contained in larger, individually dispersed melanosomes. In lighter skin, less melanin is produced, with more pheomelanin and smaller, clustered melanosomes. The final skin tone is ultimately determined by how much melanin each keratinocyte receives – nature’s own calibration of colour and protection.

Each melanin granule sits over the nucleus of a keratinocyte – ‘it’s like a hat protecting the cell’s nucleus from UV’, says Kundu. Melanin absorbs and scatters UV radiation before it can damage DNA, meaning that skin cancers are less common in people with more pigmentation. Melanin, therefore, represents a finely tuned evolutionary adaptation, not a cosmetic feature. ‘Melanin is not a flaw – it’s a function. It’s your body’s built-in sunscreen,’ says Kandu.

Melanin absorbs ultraviolet light and protects DNA from UV-induced damage, but this also means that darker skin is less efficient at synthesising vitamin D. ‘This balance between UV protection and vitamin D production is one of the evolutionary reasons for the range of human skin tones,’ says Tod. Darker skin evolved to protect against DNA damage whereas people in low UV regions like Europe have lighter skin to maximise vitamin D production. The biological advantage of melanin is UV protection – but there is a cost to that protection. There is reduced UV penetration to the deeper layers of the skin, where 7-dehydrocholesterol is converted into vitamin D₃. And crucially, this biochemical balance cannot be changed by bleaching. Lightening the skin doesn’t increase vitamin D production – it simply removes the body’s natural shield, leaving it more vulnerable to UV damage without providing any evolutionary benefit.

Why people bleach their skin

‘Everyone believes that a fairer or white skin complexion means being elite, beautiful and more accepted,’ says public health PhD researcher Rashidat Owulabi. Bleaching is less a cosmetic choice than a social contract: lighter skin is coded as status and safety, a legacy of colonial aesthetics. Women who lighten their skin are often praised for being clean or presentable, while darker skin individuals are often told to ‘tone up.’

‘40% of African women bleach … 77% in Nigeria, 59% in Togo. Skin bleaching is a multi-billion-dollar business,’ says Dellasie, a Ghanaian advocate and artist. The phenomenon extends beyond Africa – it’s common in the diaspora, and across Latin America and Asia, too.

The norm is amplified by advertising and influencers. ‘Education on skin health in Africa is minimal,’ Dellasie explains, leaving communities vulnerable to colourist messaging and unsafe products. ‘Before-and-after pictures and influencer promotions make people believe it’s safe – they become embedded ambassadors,’ adds Owulabi. The media continues to fuel the idea that lighter skin signals opportunity, desirability and employability. Branding has also evolved, moving away from explicit bleaching labels toward euphemisms like brightening, anti-ageing or anti-wrinkle – even though lab tests continue to find illegal mercury in many of these products.

Seeing the scale of the problem, Amira Adawe, founder of Beautywell, channelled her energy into advocacy. Her NGO partners with labs to test products, then simplifies and translates the findings into multiple languages so that communities can understand what’s really inside their creams. What she’s finding is alarming. ‘If you look at the global threshold [of mercury], according to the Minamata Convention, they changed in 2023 to zero parts per million. Any level of mercury is toxic,’ Adawe explains. Yet her team routinely finds products with 55,000ppm of mercury, and even those on the lower end contain around 150ppm – still far beyond legal limits. Though bans exist on paper, these products are everywhere – in corner stores, imported shipments, even rural towns with limited healthcare – and the consequences are devastating.

‘Neurological damage from heavy metal exposure does not appear for years – making the products seem harmless in the short term,’ adds Owulabi. The health effects are often invisible, making consumers underestimate the danger. Mercury in creams can even be transferred to infants through breast milk, carrying silent, long-term health risks. ‘A woman in Minnesota lost her vision … in California another was in a coma for six months. In East Africa I’ve seen women on dialysis because mercury levels … were extremely high,’ says Adawe. Mercury is cheap and fast – it suppresses melanin more, meaning the skin colour change is faster and more visible compared to hydroquinone and steroids. The impact of mercury extends to learning disabilities and speech delays.

A growing public health problem

‘The rate of kidney problems in my country is increasing by the day because of skin bleaching,’ says Joy Ikegulu, public health education research fellow and advocate in Nigeria. Studies confirmthat these products can overload the liver and kidneys. Once mercury and hydroquinone enter the bloodstream, the body relies on the renal system to remove and excrete them. Public-health agencies warn that mercury-based creams can cause irreversible renal damage, presenting with swelling around the eyes, high blood pressure and rapid weight gain. Chronic use – months of daily application – allows mercury to bioaccumulate, eventually leading to proteinuric kidney disease. Symptoms often appear only after prolonged exposure, making the danger harder to detect.

It’s no longer just a single demographic that’s vulnerable – the entire population is at risk, with mothers even buying bleaching products for their children due to family and societal pressure for acceptance. Women remain the largest user base, but male use is steadily rising, and children are being exposed through parental choices. Young girls are targeted early, scrolling through social media feeds filled with celebrities and influencers endorsing lighter skin. Ikegulu has even seen pregnant women purchasing these products in the false hope of changing their unborn baby’s complexion – a scientifically inaccurate belief that can damage the baby’s developing brain and nervous system.

Skin bleaching has become normalised and multigenerational, rooted in low self-esteem and internalised discomfort with one’s natural skin tone. ‘Everyone wants to look like a white person,’ Joy says – a disastrous remnant of colonial beauty ideals that continues to echo across generations.

Chronic users also face an unexpected side effect: a sharp, pungent body odour. ‘It’s the first thing you notice,’ says Ikegulu. When the renal system is strained, metabolic waste containing sulfur-rich amino acids is released through sweat. Meanwhile, hydroquinone oxidises into quinones and phenolic compounds – giving off a harsh chemical smell, especially in humid climates. The visible skin blotching and odour that follow can trigger anxiety, depression and isolation, compounding the harm.

‘Many countries banned mercury and hydroquinone, but enforcement is almost zero,’ says Adawe. Loose policy allows anyone to mix a cocktail of harmful chemicals, and people will buy it. Imports and online sales persist, even in regions where other essentials are scarce. The products are easy to find – and until that changes, so will the damage.

How skin bleaching agents work

Bleaching agents work by blocking or slowing down tyrosinase – the key enzyme responsible for melanin production. ‘Creams can be absorbed … into the top layer of skin, the epidermis,’ explains Kundu. On a microscopic scale, chronic bleaching can reduce melanin synthesis permanently by damaging melanocytes, the pigment-producing cells. These products target different stages of the pigment pathway – during melanin synthesis, melanosome formation and transfer, or epidermal turnover, where they accelerate the shedding of pigmented skin cells.

‘There are several skin-lightening agents on the market. They work at different points in the production of pigmentation,’ says Tod. The most common ingredients – hydroquinone, kojic acid and thiamidol – all interfere with tyrosinase, effectively switching off the body’s natural pigment factory and disrupting the very process that gives skin its colour and protection.

Hydroquinone acts as a structural analogue of tyrosine, effectively tricking the enzyme into producing toxic quinones that damage the melanocyte itself. It can act aggressively and permanently, causing serious side effects. Long-term misuse leads to exogenous ochronosis – an irreversible dermal pigmentation disorder. ‘The skin turns a very unusual pinkish colour … with caviar-like stippling,’ explains Kundu.

Mercury salts replace the copper cofactor in tyrosinase, shutting down its activity and halting melanin synthesis. But mercury is far more than a pigment inhibitor – it is a potent neurotoxin that is systemically absorbed, damaging the kidneys and nervous system. ‘Mercury is readily absorbed by the skin and is particularly toxic to the kidneys, nervous system and developing foetuses,’ says Tod. Mercury exposure also increases UV vulnerability, leaving the skin photosensitive and more prone to cancer.

Topical steroids are another cause for concern. They aren’t true depigmenters, but long-term use thins the skin, destroying collagen and elastin, leading to fragile, prematurely aged skin, stretch marks, acne and easy bruising. Other agents, such as retinoids, increase cell turnover, causing pigmented keratinocytes to shed faster and making the skin appear lighter temporarily. Retinoids themselves aren’t systemic toxins, but in unlabelled combinations, they amplify irritation and barrier damage.

Clinically treating pigment problems

There are, however, several naturally occurring pigment disorders that dermatologists treat medically rather than cosmetically. Melasma – driven by UV exposure and hormones – causes patchy overproduction of melanin, often on the face. Vitiligo is the opposite, a depigmentation condition caused by loss of melanocytes. Post-inflammatory hyperpigmentation (PIH) develops after acne, eczema or bites, when, as Kundu explains, ‘trauma pushes melanin to the wrong places’.

Treatment for these conditions focuses on repair, regulation and protection – not erasure. Daily high-SPF photoprotection is ‘the most critical step’, says Adawe. Dermatologists often prescribe time-limited cycles (around three months) of hydroquinone with retinoids and mild corticosteroids for melasma or PIH, followed by a rotation to alternatives to avoid the risks of long-term exposure. These substances are safe only when treating disease, not for lightening normal skin, and must be supervised.

‘Tretinoin … helps the skin turn over, so you’re sloughing off some extra melanin that’s moved up in the skin,’ Kundu explains. Tretinoin – also known as retinoic acid – is one of the most prescribed topical agents in the world, bridging pigment control and skin repair by stimulating collagen renewal. Dermatologists also prefer reversible, cosmetic-level inhibitors such as Thiamidol, which act on human tyrosinase without permanently altering melanocytes.

Thiamidol, marketed as a safer alternative, works by selectively inhibiting human tyrosinase – the key enzyme in melanin production – with reversible action. ‘It does not induce lightening of the entire skin. It targets areas with excessive melanin production,’ says Ludger Kolbe, chief scientist for photobiology at skin care company Beiersdorf.

When melanin is suppressed, the skin loses part of its protective structure

Beiersdorf positions Thiamidol as a targeted hyperpigmentation active ingredient, not a whole-skin lightener – a clear statement that the company is not pro-bleaching but focused on medical-grade pigment care. ‘Its mechanism differs from bleaching agents such as hydroquinone,’ Kolbe explains. He describes Thiamidol as the first and only inhibitor designed specifically for and tested on human tyrosinase, capable of reducing existing pigment spots while helping to prevent new ones. Crucially, he adds, ‘the mode of action is reversible … melanocytes will restart melanin production after discontinuation’.

Dermatologists like Kundu agree that these medications can be used safely under medical supervision, but she cautions that misuse or combining multiple actives can overwhelm the skin barrier, leading to a range of problems. ‘When melanin is suppressed, the skin loses part of its protective structure. You see more inflammation, more infections and, paradoxically, more pigment problems later,’ Kundu warns. Melanin, she reminds us, ‘is a living system, not a pigment you can safely switch off indefinitely’.

The cost of beauty?

The biggest issue lies in accessibility – these products are everywhere: on the shelves of corner stores, in open-air markets and easily available online. Availability drives use. Many of the creams sold in local markets are spiked with steroids and mercury, and clinicians consistently warn against over-the-counter ‘lighteners’. Adawe’s team has tested products sourced from both the US and East Africa and found almost identical formulations across regions – many also contain other heavy metals such as lead and arsenic. Worse still, mercury can contaminate household air, lingering even after use stops and affecting other family members.

Governments are finally beginning to act. Regulators are far more engaged than a decade ago. Adawe now trains border and customs teams, urging for stronger legislation and continuous enforcement. ‘If there’s not enforcement, policy is not active.’ Some countries are beginning to see progress – Rwanda, for example, has stricter compliance, meaning fewer products reach the shelves and, as Owulabi notes, ‘has lower prevalence’ of the associated problems.

Retail platforms like Amazon and eBay are also starting to respond. After Adawe’s petitions, ‘some listings were removed, though others have never listened’, she says of major online retailers where many of these products can still be found and purchased with ease.

At the community level, Ikegulu continues to advocate for natural methods, urging people to stop trying to change their baseline skin colour. She preaches the benefits of natural remedies like cocoa butter, especially for melanin-rich skin, which can repair the skin barrier, soothe irritation, and help maintain an even tone by preventing secondary inflammation. However, Owulabi insists that telling people to stop must come with safer alternatives. ‘When you have people stop something, you must create a better alternative … health promotion and public health awareness are key.’

Alternatives already exist – but only when the goal is treating disease, not altering natural colour. A major part of that education is differentiating medicine from bleach. Treating clinical conditions chemically should never be conflated with whole-skin lightening. There also needs to be greater ingredient transparency to curb vague ‘brightening’ claims that allow unsafe products to slip through regulation. Demand persists, but Kundu believes it can be redirected: ‘reframing toward safe medical treatment redirects patients’, says Kundu.

There is no silver bullet for pigmentation. ‘The sheer number of depigmenting agents tells you that nothing is a wonder cure. Prevention is the most critical step, in the form of sun protection,’ says Tod. No single ingredient is inherently safe; its safety hinges on supervised, time-limited regimens and strict photoprotection.

Ultimately, lasting change will only come from acceptance and pride in natural skin colour. As Dellassie argues, we must confront a ‘toxic and outdated psychology’ that equates lightness with value. That means campaigns, particularly on social media, to challenge colourist narratives so that young people aren’t influenced by damaging messages about skin tone. There are signs of hope – mentorship programmes, youth groups, and community interventions are slowly shifting attitudes – but, as Adawe warns, ‘we will continue to see skin lightening products until we dismantle colourism and redefine beauty standards’.

Zahra Khan is a science writer based in London, UK