Menthol
Applications
In nonprescription products for short-term relief of minor sore throat and minor mouth or throat irritation. Examples: lip balms and cough medicines. As an antipruritic to reduce itching. As a topical analgesic, it is used to relieve minor aches and pains, such as muscle cramps, sprains, headaches and similar conditions, alone or combined with chemicals such as camphor, eucalyptus oil or capsaicin. In Europe, it tends to appear as a gel or a cream, while in the U.S., patches and body sleeves are very frequently used. Examples: Tiger Balm, or IcyHot patches or knee/elbow sleeves. As a penetration enhancer in transdermal drug delivery. In decongestants for chest and sinuses (cream, patch or nose inhaler). Examples: Vicks VapoRub, Mentholatum, VapoRem, Mentisan. In certain medications used to treat sunburns, as it provides a cooling sensation (then often associated with aloe). In aftershave products to relieve razor burn. As a smoking tobacco additive in some cigarette brands, for flavor, and to reduce throat and sinus irritation caused by smoking. Menthol also increases nicotine receptor density, increasing the addictive potential of tobacco products. Commonly used in oral hygiene products and bad-breath remedies, such as mouthwash, toothpaste, mouth and tongue sprays, and more generally as a food flavor agent; such as in chewing gum and candy. As a pesticide against tracheal mites of honey bees. In perfumery, menthol is used to prepare menthyl esters to emphasize floral notes (especially rose). In first aid products such as "mineral ice" to produce a cooling effect as a substitute for real ice in the absence of water or electricity (pouch, body patch/sleeve or cream). In various patches ranging from fever-reducing patches applied to children's foreheads to "foot patches" to relieve numerous ailments (the latter being much more frequent and elaborate in Asia, especially Japan: some varieties use "functional protrusions", or small bumps to massage one's feet as well as soothing them and cooling them down). In some beauty products such as hair conditioners, based on natural ingredients (e.g., St. ⁠Ives). As an antispasmodic and smooth muscle relaxant in upper gastrointestinal endoscopy. In organic chemistry, menthol is used as a chiral auxiliary in asymmetric synthesis. For example, sulfinate esters made from sulfinyl chlorides and menthol can be used to make enantiomerically pure sulfoxides by reaction with organolithium reagents or Grignard reagents. Menthol reacts with chiral carboxylic acids to give diastereomic menthyl esters, which are useful for chiral resolution.
Menthol-23