Hydroquinone is a topical agent for reducing skin pigmentation. It is available in over-the-counter strength of up to 2 percent and higher concentrations by prescription. People typically use hydroquinone to lighten areas of skin affected by hyperpigmentation disorders, as well as for freckles and age spots. Hydroquinone also is a component of the herbal remedy uva ursi. Because of dangers associated with the substance, several countries have banned hydroquinone, and the U.S. Food and Drug Administration (FDA) has proposed a ban on most prescription and over-the-counter hydroquinone products.
The FDA and standard-setting agencies of several other countries have cited a skin condition called ochronosis as a concern with hydroquinone use. Although uncommon, particularly with over-the-counter strength preparations, some people have developed a blue-black skin discoloration after using hydroquinone bleaching creams. Ochronosis also can cause gray-brown spots and tiny, yellow-to-brown bumps, as well as skin thickening. The condition is mainly associated with dark-skinned people using hydroquinone in high concentrations for long time frames.
Hydroquinone topical solutions can make skin more sensitive to sunlight (photosensitivity). People using these preparations should avoid exposure to sunlamps and tanning beds and wear protective clothing and sunscreen when in sunlight. Exposure to ultraviolet light can cause severe sunburn when using hydroquinone. Applying hydroquinone to skin that is sunburned, windburned, chapped or irritated can worsen these conditions.
Rodent studies involving very high doses of hydroquinone administered by feeding tube showed the potential to cause cancer, according to the FDA report on hydroquinone skin bleaching products. No carcinogenic properties have been associated with topical or oral hydroquinone use in humans.
Although unlikely, some people may experience an allergic reaction to hydroquinone. Signs as listed by Drugs.com include severe burning or stinging sensations, hives, breathing trouble, and facial, throat or mouth swelling. An allergic reaction to hydroquinone should be considered a medical emergency.
When taken orally in large amounts, as in uva ursi, hydroquinone is toxic, states Drugs.com. It may cause ringing of the ears, nausea, seizures and bluish skin due to insufficient oxygen in the blood (cyanosis). Large amounts of oral hydroquinone also can cause liver damage. The University of Maryland Medical Center recommends taking uva ursi for no longer than five days and no more than five separate times in a year.