2.  A “depilatory” can truly be categorised as a cosmetic, since it beautifies by removing unsightly hair from certain parts of the body.  The term depilatory must therefore be reserved for chemical means of hair removal from skin (in particular superfluous hair occurring on the face, legs, axilla etc), without causing any injury to the skin. It is definitely different from other methods of hair removal, which includes,  Mechanical removal of hair.  Destruction of hair by electrolysis, by use of laser energy or diathermy.  Shaving.

3. Chemistry of hair & its removal:  Hair mainly consists of amino acids, mainly cysteine and most of these amino acids containing sulphur constitute a group of proteins, known as Keratin.  Electrolysis is a suitable method for permanent removal, but is slow and costly.  The other electrical methods consist of the use of galvanic current and high frequency current. The galvanic method consists of passing direct current through one or more special needles inserted at the hair follicle and destroy hair permanently. The method is slow, but yields good results.  More recently, the use of high frequently current has been found to be quite safe and satisfactory.  The removal of hair by x-rays is very dangerous, as these rays also destroy the skin/tissue surrounding the hair, and thus, this method should not be recommended.

4. Regarding hair removal, two topics deserve special mention, a) Disguising b) Epilation a) Disguising:  Instead of superfluous hair being removed, they can be disguised in such a way that they become less noticeable and thus blend with underlying skin.  Thus men can resort to a “quick-shave” (when they do not wish to shave) by covering the hair stubble on their faces with a colored men’s talc or other powder.  Women usually resort to cake make-up and the liquid powders to disguise hair. When the hair is dark, women like to bleach them by cleaning it first, followed by the use of peroxides and diluted ammonia water.

5. b) Epilation:  Epilation simply consists of trapping the hair in a viscous adhesive mass and then using physical force to pull the trapped fibre from its body anchor.  Some benefits can be seen by “hot” processes where warm wax is allowed to cool on the skin. It is also customary to add benzocaine, a local anesthetic, to certain formulation to reduce the pain. Ingredients: The ingredient basis for cosmetic epilating products mainly include rosin (colophony), bees wax and viscous sugar composition. They form a sticky mass, usually grips the hair but has less adhesion to the skin.

6. Ex: Epilating wax; Formula % Light colored rosin 52 Yellow bees wax 25 Paraffin 17 Petrolatum 5 Perfume 1 Method: Melt the waxes and the rosin and add petrolatum. Cool to around 60˚ and then mix the perfume, pour the melted mass into a suitable moulds. When this wax is used, it is melted and painted over the surface to be de haired.

7. Depilation:  Depilatories are the preparations used for degradation of the superfluous hair chemically without affecting the skin.  Depilatory removes the hair at the neck of the hair follicle and thus has advantage over razor shaver which removes hair on a level with the surface of the epidermis.  The depilatories act by degrading the hair Keratin. As it is known that Keratin is sensitive to the action of strongly alkaline aqueous solutions and reducing agents, most of the depilatories consist of such agents.  Thus, the qualities of an ideal depilatory should be as follows,  Non-toxic and non-irritant to skin.  Fast and efficient in action, causing depilation within 5 minutes.  Preferably odourless.

8.  Should be stable upon storage.  Non-staining/damaging to clothing.  Cosmetically elegant. Formulation of depilatories: Chemical depilatories are sold in the form of liquids, pastes and powders. Typical ingredients of a chemical depilatory include,  Alkaline reducing agents  Perfumes  Emulsifiers  Emollients

9.  Thickening agents  Humectants  Miscellaneous agents Alkaline reducing agents: Depilatory preparations usually contain an alkaline reducing agent as their active component. These agents will cause the hair fibres to swell and cleave the cystine bridges between adjacent polypeptide chain, causing degradation of hair. Eg: Sulphides, Stannites etc.

10. Perfumes: Most of the alkaline reducing agents, including salts of thio glycolic acid, have usually an odour of their own, hence, the use of perfumes is almost a necessity in depilatory products. Eg: Aromatic alcohols, Rose, Saffron etc. Emulsifiers: Emulsifiers are used for cosmetic elegancy and potential irritancy. Eg: Sodium lauryl sulphate, Ethylene oxide ethers etc. Emollients: The common emollients are mineral oils and paraffins.

11. Thickening agents: The synthetic thickening agents such as methyl, hydroxy ethyl or carboxy methyl cellulose are used. These are used to make paste of requisite consistency. Humectants: Humectants are incorporated to prevent quick drying on the skin. Eg: Glycerine, Sorbitol, Propylene glycol etc. Evaluation of depilatory efficacy: 1) Tensile kinetics method: In this method, stress decay caused by disulfide bond reduction is measured, using commercial instruments such as tensile strength tester, an optical diameter gauging system and an electro balance. The time required to reduce the stress supported by hair by 95% (T 95 %) was shown to correlate to in-vivo hair removal rate in commercial products.

12. 2) HPLC Method: This method distinguish between thio glycerol, thiolactic acid and thio glycolic acid. It results an yellow derivative, permitting HPLC detection at 464 nm. The procedure is most suitable for aqueous preparation, including o/w creams and lotions. 3) Thermo mechanical method: In this method a thermo mechanical analyzer is used to measure the time at which a hair bundle, under constant stress and immersed in depilatory, begins to stretch. The test is carried out under isothermal conditions and indicate good precisions, which can be correlated with results on animals.