The use of skin lighteners through both topical (eg. creams) and intravenous (through a shot in the vein) applications have been documented on nearly every continent. Common skin lightening agents – such as glutathione, hydroquinone, mercury, retinoids, and steroids – inhibit the production of melanin, the group of natural pigments that gives color to eyes, hair, and skin. All of these skin lightening agents have been associated with negative effects. Most notably, products that contain hydroquinone have been found to be associated with squamous cell carcinoma, the second most common form of skin cancer, through case reports.

Due to mixed evidence, hydroquinones are not currently classified as carcinogens. However, accumulating evidence connects it to possible DNA damage and immunosuppressive responses. At this time, more research is needed to clarify the relationship between hydroquinone and the risk of developing skin cancer.

Paradoxically, the use of creams that contain hydroquinone may lead to exogenous ochronosis – a blue-black darkening of the skin in the area where it is applied that cannot be reversed. Other side effects of topical hydroquinone use are acne, contact dermatitis, conjunctival and nail hyperpigmentation, stretch marks, and skin infections.

Other skin lightening agents also cause side effects. For example, glutathione can cause abdominal cramps and trouble breathing in addition to other side effects, and skin-lightening retinoids can cause burning, itching, stinging, scaling, and redness of the skin in addition to other side effects.

In some countries, skin lighteners may be available for over-the-counter purchase in major retail stores. Active ingredients, such as hydroquinone, may be present in amounts that are regulated by national health and pharmaceutical authorities. However, in attempts to obtain faster results, consumers may apply more product than recommended for correct usage, which can increase the risk of experiencing negative side effects.

In the European Union, Japan, Côte d’Ivoire, Ghana, Rwanda, South Africa, Australia, and the U.S., hydroquinones are not authorized for cosmetic skin lightening or such products are banned. However, research and investigative journalism have shown people seeking out products in the black market where skin lighteners are banned or unaffordable, and illegal skin-lightening products being sold without being licensed or tested.

This problem is partially because products are not always tested or closely monitored by regulatory agencies. For example, The U.S. Food and Drug Administration (FDA) banned mercury in skin-bleaching or lightening products in 1990; however, tests run May 2011 the Minnesota Department of Health (MDH) found that some products that are still readily available contain mercury at levels much higher than what the U.S. Food and Drug Administration (FDA) allows.

The U.S. FDA cautions that unapproved products are potentially ineffective and may contain unknown or unsafe ingredients. Additionally, experts warn against using homemade skin lighteners, as they may also result in exogenous ochronosis.

Skin lighteners may be used under the strict supervision of a dermatologist to treat acne, age-related hyperpigmentation, melasma, or vitiligo. However, consumers may use skin lightening and bleaching products for cosmetic purposes to improve skin tone or texture. Due to light skin being often idealized as the pinnacle of beauty, use of skin lighteners is also driven by desires to satisfy peers, elevate one’s social status, and increase employment opportunities. These pressures to have a lighter skin tone affects the self-esteem for women of color around the world and makes them more likely to use skin lightening products.

Dermatologists have expressed concern over the potential long-term health consequences, like skin and breast cancers, that lightening products contribute to. Currently, studies on skin bleaching products focus primarily on the side effects of single ingredients. A better understanding of the impact of entire product formulations is needed. Researchers have also called for an evaluation of the potential carcinogenic effect of inhibiting melanin production due to skin lightening.