The following statement is from The U.S. Food and Drug Administration:
The U.S. Food and Drug Administration (FDA) is warning the public that the use of benzocaine, the main ingredient in over-the-counter (OTC) gels and liquids applied to the gums or mouth to reduce pain, is associated with a rare, but serious condition. This condition is called methemoglobinemia and results in the amount of oxygen carried through the blood stream being greatly reduced. In the most severe cases, methemoglobinemia can result in death.
Benzocaine gels and liquids are sold OTC under different brand names such as Anbesol, Hurricaine, Orajel, Baby Orajel, Orabase, and store brands. Benzocaine is also sold in other forms such as lozenges and spray solutions (also see separate Drug Safety Communication on Benzocaine Sprays1). These products are used to relieve pain from a variety of conditions, such as teething, canker sores, and irritation of the mouth and gums.