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Hair
removal by chemicals
The earliest means of chemical hair removal dates back to the
ancient Turks, who used a concoction known as "rusma".
Rusma was a combination of yellow sulfide of arsenic, quicklime,
and rose water. It worked reasonably well, but because of its arsenic
content it is not recommended today! Modern chemical hair removal
products come as creams, gels, aerosols, or roll ons but the active
ingredients in chemical depilatories have not really changed much
over the last 50 years. The key ingredient is some kind of alkali
in solution. Common chemicals found in chemical depilatory products
can be classed into three main groups; hydroxides (calcium hydroxide,
potassium pydroxide, sodium hydroxide), thioglycolates (sodium thioglycolate,
calcium thioglycolate, thioglycolic acid) or occasionally sulfides
(barium sulfide). The products may also include glycols or urea
in an additional, supporting role.
The principle by which they work is simple. Hair fiber is mostly
made from keratin proteins. Keratin in hair contains a lot of the
amino acid cysteine. Cysteine is important because it contains sulfur
molecules. Sulfur molecules on one keratin protein chain and bind
to other sulfur molecules on adjacent keratin proteins. These chemical
bonds give hair its strength and resistance to degradation. Hair
is not significantly damaged by acids but disulfide bonds can be
quickly broken apart by alkali solutions (hydrolyzed). Essentially
this is what all chemical depilatories are, an alkali in solution.
The alkaline cream or gel is applied to the skin to cover the hair.
The alkali penetrates into the hair fiber and breaks up the disulfide
bonds between the keratin proteins. This severely weakens the hair
such that when the cream or gel is washed away the hair is washed
away too.
Because the cream or gel is applied on the skin surface, it is
mostly focused at the opening of the hair canal and causes the greatest
weakening of the hair fiber at this point. When you wash the skin
clean the hair is most likely to break at this weak point. Compared
to shaving, this brings the advantage of a smoother result. The
hair breaks at a point just slightly below the hair canal opening.
The rest of the hair is still protected in the hair follicle canal
and remains undamaged. The hair will continue to grow, but it takes
a few days for the hair in the canal to grow up and become exposed
above the skin surface. So compared to shaving the skin stays smoother
for longer.
The greatest problem with hair depilatory creams is
that their chemical nature can be quite irritating to sensitive
skin. Skin around the groin and the face is particularly sensitive,
although there are mild depilatory creams available for these sensitive
areas. The other risk with depilatory cream use is the development
of ingrowing hair. Because the hair fibers are broken off at slightly
below the skin surface, the remaining hair in the hair follicle
canal has the opportunity to dig into the skin surrounding the canal
opening causing focal inflammation. People with curly leg hair who
remove it with depilatory creams are more at risk of developing
ingrowing hairs than those with straight leg hair.
For these reasons if you decide to use a depilatory
cream, you should first test it to make sure your skin does not
adversely react to the alkali and that you do not develop ingrowing
hair. Use the depilatory on a small area of skin first and see what
happens. Wait a few days and if everything seems okay then use the
depilatory over the full area you wish to treat.
Hair
removal by chemicals references
- Le Coz CJ. Contact nummular (discoid) eczema
from depilating cream. Contact Dermatitis. 2002 Feb;46(2):111-2.
- Olsen EA. Methods
of hair removal. J Am Acad Dermatol. 1999 Feb;40(2 Pt 1):143-55
- Fisher AA. Unique reactions of scrotal
skin to topical agents. Cutis. 1989 Dec;44(6):445-7.
- Klein AW, Rish DC. Depilatory and shaving
products. Clin Dermatol. 1988 Jul-Sep;6(3):68-70.
- Natow AJ. Chemical removal of hair. Cutis.
1986 Aug;38(2):91-2.
- Yamasaki R, Dekio S, Jidoi J. Allergic
contact dermatitis to ammonium thioglycolate. Contact Dermatitis.
1984 Oct;11(4):255.
- Foussereau J, Maleville J, Grosshans E,
Araujo A, Maillot C, Basset A. [Allergic eczema caused by thioglycerin
in depilatory creams. Disadvantages of this substance in cosmetology]
Bull Soc Fr Dermatol Syphiligr. 1967;74(6):762-6.
- Webber MG. O-T-C depilatories. J Am Pharm
Assoc. 1967 Jul;7(7):384-5.
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