An amino acid that may reduce the likelihood of herpes simplex outbreaks. Some lubricants include l-lysine for this reason.

L-lysine is found naturally in soybeans, lentils, and other popular foods, and it is an important building block for proteins. It may also have beneficial effects on skin health, although there is limited research to support this use.

People with herpes are much more likely to transmit the virus during outbreaks, and l-lysine may help to control the spread of the disease. However, it is important to note that l-lysine does not provide complete protection against genital or oral herpes, particularly during an outbreak; condoms and dental dams are the best way to limit the spread of the herpes simplex virus, and products with l-lysine should only be used as a secondary form of protection.