Mequinol is a common active ingredient in topical drugs used for skin depigmentation. As a topical drug mequinol is often mixed with tretinoin, a topical retinoid. A common formulation for this drug is an ethanolic solution of 2% mequinol and 0.01% tretinoin by mass. Dermatologists commonly prescribe the drug to treat solar lentigines, liver spots, or age spots.
In organic chemistry 4-methoxyphenol is used to inhibit the radical polymerization of monomers (e.g. acrylates or styrene monomers).