Chemical depilatory
Achemical depilatoryis acosmeticpreparation used toremove hairfrom theskin.Common active ingredients are salts ofthioglycolic acidandthiolactic acids.These compounds break thedisulfide bondsinkeratinand alsohydrolyzethe hair so that it is easily removed. Formerly,sulfidessuch asstrontium sulfidewere used, but due to their unpleasant odor, they have been replaced bythiols.[1]
The main chemical reaction effected by the thioglycolate is:
- 2 HSCH2CO2H (thioglycolic acid) +R-S-S-R (cystine) →HO2CCH2-S-S-CH2CO2H (dithiodiglycolic acid) +2 RSH (cysteine)
Chemical depilatories contain 5–6%calcium thioglycolatein acreambase (to avoid runoff).Calcium hydroxideorstrontium hydroxidemaintain a pH of about 12. Hair destruction requires about 10 minutes. Depilation is followed by careful rinsing with water, and various conditioners are applied to restore the skin's pH to normal. Depilation does not destroy thedermal papilla,and the hair grows back.[2]
Chemical depilatories are available ingel,cream,lotion,aerosol,roll-on, andpowderforms. Common brands includeNair,Magic Shave,andVeet.
Chemical depilatories are indicated in the treatment ofhirsutisminpolycystic ovary syndrome.
Depilatory ointments, or plasters, were known to Greek and Roman authors aspsilothrum.[3]In Jewish lore,King Solomonis said to have discovered a chemical depilatory made from a mixture of lime and water andorpiment(arsenic trisulfide).[4]
References[edit]
- ^"Hair Preparations",Ullmann's Encyclopedia of Industrial Chemistry(7th ed.), 2007,doi:10.1002/14356007.a12_571.pub2
- ^Arza Seidel; et al., eds. (2013),Kirk-Othmer Chemical Technology of Cosmetics,p. 44
- ^"PSILOTHRUM",Dictionary of Greek and Roman Antiquities(3rd ed.), 1890
- ^Colloquy of the Queen of Sheba,taken from the AramaicTargum Sheni of Megillat Esther.
