Hydroquinone is a topical lightening agent for the skin that works by inhibiting the enzyme tyrosinase that converts DOPA to melanin thus decreasing melanocyte production. It is available in up to 2% formulation over the counter but 4% or higher by prescription. It is typically applied two times per day, and it is important to use good sunscreen whenever it is in use. Hydroquinone should not be used continuously and typically is used in a 3 months on and 3 months off approach. This is to avoid possible side effects such as irritation, stinging, redness, or ochronosis which is a bluish black discoloration secondary to deposition of homogentisic acid in the skin. Ochronosis is difficult to treat and best to be prevented.