Chemical Depilatories

Chosica Buffet, MD¹ and Jaggi Rao, MD, FRCPC²

¹Resident, University of Saskatchewan
²Faculty Dermatologist, University of Alberta

Introduction

There is a growing demand for the removal of unwanted facial and body hair in both men and women. The desire for hair removal is primarily for cosmetic and personal preference but in some cases there may be excessive hair growth that is secondary to systemic disease, hormonal alterations, and certain medications.¹ There are numerous hair removal methods which can be grouped either as temporary or permanent. Chemical depilatories have existed since ancient times as a temporary hair removal method.² Currently, several types of depilatory agents are available. They are commonly used, simple to apply, inexpensive and readily available. This article reviews their method of action, characteristics, advantages and disadvantages.

Method of Action

• Depilatories work by breaking down the keratin structure of the hair by inducing chemical reactions.
• Keratin is a structural protein that gives the hair its strength and is stabilized by disulphide bonds.^3,4
• All depilatories function by disrupting the disulphide bonds which then destabilizes keratin.² This weakens the hair so it can then be easily wiped off the surface of the skin.
• The difficulty in producing good depilatory agents arises from the fact that keratin is also found in the skin.
• The active ingredients in depilatories must preferentially target the keratin in the hair in order to be effective and decrease the risk of side effects on the skin (Table 1).³
• Fortunately, the skin is generally less susceptible to depilatory agents as it contains less disulphide bonds.⁵
• The most commonly used depilatory agents are thioglycolates and to a lesser extent, sulphides.^5-7
• The efficacy is increased in products which combine a strongly alkaline (basic) effect with a strongly deoxidizing reaction, hence their being combined with metal hydroxides.³

Chemical Composition of Depilatories

Thioglycolate-based Depilatories

• The most common active ingredient in chemical depilatories is thioglycolate (2-10%) mixed with calcium, sodium or potassium hydroxide (2-6%).²
• Calcium thioglycolate is the least irritating salt form. Its efficacy does not increase at a concentration of more than 4% and may be more irritating.⁷
• These preparations have an elevated pH (pH12-13) as alkalinity improves the efficacy of thioglycolate in dissolving disulphide bonds.³
• The strongly alkaline solution has two further functions:
  • it opens up the structure of the hair to allow the aqueous solution to penetrate and reach disulphide bonds;
  • it affects other bonds within keratin, further breaking apart its structure.
• When enough chemical bonds are broken, the hair can be wiped or washed off where it emerges from its follicle.²
• Health Canada permits thioglycolic acid at concentrations ≤5% with a pH of 7-12.7 in depilatory products.⁸

Health Canada permits thioglycolic acid at concentrations ≤5% with a pH of 7-12.⁷ in depilatory products.⁸

• These depilatories have a similar mechanism of action as thioglycolate-based depilatories.
• Preparations include strontium, calcium and barium sulphide.⁷
• They are all powder-based depilatories, which are mixed in equal parts with water.
• Sulfide-based depilatories are stronger, faster-acting, and more effective hair removers but are more irritating to the skin and must be used with care.^5,9
• This class of depilatory is ideal for individuals with dark and coarse hair, such as those of African descent.⁹

Recommendations and Usage

• Any depilatory should be tested first on a small non-facial area of the skin 24-48 hours before general use. If an allergic reaction or significant irritation occurs, such as redness or itching, the product should not be used.^3,7
• Depilatories should be applied to the skin at room temperature.
• Longer hair that will be treated should be trimmed short.
• The depilatory must be left on the skin for about 3-15 minutes, depending on the depilatory agent and the coarseness of the hair.²
• The weakened hair becomes gelatinous and the hair and depilatory should then be wiped off and the skin washed off with soap and water.⁷
• Burns or skin irritation may occur if the depilatory is left on longer than the manufacturer’s recommended time.
• Applying a hydrocortisone cream (~1%) or an acidic emollient after hair removal may decrease potential skin irritation.⁷
• Emollients include: CeraVe® moisturizing cream, Vaseline® lotion, Aveeno® daily moisturizing lotion, Cetaphil® moisturizing cream, etc.
• Depilatory formulations are specifically designed for specific skin areas and should not be interchanged.⁵
• They should not be used on the face unless specifically indicated.
• The product should not be used in patients with dermatological problems, nor should they be applied to broken, irritated or sunburnt skin.^3,5
• If the skin begins to sting, burn or itch during use, the depilatory must be washed off immediately, as the skin is becoming irritated.³

Indications

• Although chemical depilatories are generally used for cosmetic reasons, they are also indicated for hair removal in individuals with pseudofolliculits barbae, hypertrichosis and hirsutism.^4,6,11 The latter two conditions usually require medical treatment and will not be discussed at this time.

Pseudofolliculitis Barbae

• Depilatories are used to treat pseudofolliculitis barbae, an inflammatory skin condition commonly found in men due to ingrown facial hairs which can result from shaving. This is particularly common in individuals with coarse or curly hair.
• Depilatory agents are effective because they leave the distal ends of the hairs with soft, brush-like tips rather than the sharp tips produced by shaving which tend to ingrow.^9,12
• Stronger depilatories, such as sodium hydroxide, potassium hydroxide, strontium sulphide and barium sulphide, are often needed due to the coarseness of the hair.⁹ These stronger agents are more irritating to the skin and must be used with care.⁹

Selecting a Depilatory

• Depilatory creams are available in a variety of vehicles including: cream, gel, lotion, aerosol, roll-on, and powder forms.
• Creams and lotions are widely available but care must be taken to spread them evenly.
• Gels are a good alternative for those who do not like creams.
• Roll-on creams are neater to apply but may not come out as thick as needed.
• Aerosols are quick and easy to apply but care must be taken not to miss an area.
• Powders are easy to apply on the face and are typically used by men for the beard region.
• Numerous depilatory creams have been developed for men as well as women.
• There are numerous formulations that target different body areas.
• The concentration, pH, salt composition, and vehicle of a formulation is designed for a specific skin area or hair type.^4,5

Skin Area

• Face
• Arms
• Axillae
• Legs
• Bikini area
• Back and chest

Hair Type

• Fine to medium hair
• Medium to coarse hair

When Recommending a Cream

• Consider if the patient has a history of skin sensitivity or allergies.
• Some creams are formulated specifically for sensitive skin and include agents such as moisturizers and aloe to soothe irritated skin.
• If the patient has a history of skin allergic reactions, they should consult their physician.

Commonly Available Depilatory Brands

• Veet®
• Nair®
• Magic® Shave
• Olay®
• Bikini Zone®
• Andrea

Advantages

• Inexpensive
• Readily available²
• Easy and quick to apply⁷
• Can be done at home
• Pain free method²
• Longer lasting and softer hair regrowth when compared to shaving as the depilatory can settle deeper in the follicles, dissolving the hair at a deeper level.⁶
• Mild exfoliating effect leading to brighter and smoother skin.
• Removal of ingrown hairs.⁹

Disadvantages

• A temporary method of hair removal–lasting up to 10 days.⁷
• Have an unpleasant odour due to sulphur containing
  compounds in depilatories.⁷
• Can be messy
• May cause skin irritation including redness, burning, and
  itching if they are left too long or used inappropriately.^4,6
• May cause irritant and allergic contact dermatitis.⁵

Side Effects

• Irritant contact dermatitis (1-5%)
  • Is the most common side effect due to the high alkalinity
    of depilatories.⁷
  • May be avoided with the use of a topical corticosteroid
    applied after hair removal.^5,7
• May be controlled by:
  • Decreasing the frequency of use.
  • Selecting a different vehicle (gel, lotion, cream).
  • Using products with a lower concentration of active
    ingredient or lower pH.
• Allergic contact dermatitis is rare and usually caused
  by fragrances, lanolin derivatives or the thioglycolate
  compound.^5,7
• In an effort to decrease the risk of skin irritation, some
  products include post-treatment moisturizing creams,
  moisturizers in the depilatory creams, or a barrier-type
  substance to be applied to the skin prior to depilatory use.

Future Developments

• Lowering the pH of depilatory creams without increasing depilation time would be ideal as it would decrease the negative effects of these agents on the skin.
• A recent study suggests that decreased depilatory effect due to reduced pH could be compensated for with the addition of novel penetration enhancers such as ethanol, dimethyl sulfoxide, and peppermint oil.¹³ These enhancers were found to decrease depilation time and could eventually be incorporated in new lower pH formulations without affecting depilatory time.

Conclusion

The use of depilatories is rapidly growing and becoming widely accepted as a temporary hair removal solution. Their ease of use, widespread availability and broad product range has increased their popularity with consumers. Improvements in their formulation is associated with good cosmetic results have positioned them to become one of the most used methods of hair removal in North America.

References

1. Ramos-e-Silva M, et al. Clin Dermatol. 2001;19(4):437-444.
2. Fernandez AA, et al. Cosmet Dermatol. 2013;12(2):153-162.
3. Ejersted A, et al. Survey of Chemical Substances in Consumer Products: Analysis of chemical hair-removal products. Survey no.31. Danish Environmental Protection Agency. 2003.
4. Blume-Peytavi U. Br J Dermatol. 2011; 165 Suppl 3:19-23.
5. Draelos Z. Curr Probl Dermatol. 1995;7(2):45-64.
6. Fisher EJ, et al. J Am Acad Dermatol. 2006; 55(2):320-323.
7. Olsen EA. J Am Acad Dermatol. 1999; 40(2 Pt 1):143-155.
8. List of Prohibited and Restricted Cosmetic Ingredients (The Cosmetic Ingredient Hotlist). Health Canada. March 2011: p31
9. Cole PD, et al. Semin Plast Surg. 2009; 23(3):168-172.
10. Toedt J, et al. Chemical Composition of Everyday Products. Westport; London: Greenwood Press, 2005.
11. Lapidoth M, et al. Dermatology. 2010;221(1):34-42.
12. Kelly AP. Dermatol Clin. 2003; 21(4):645-653.
13. Moghimi HR, et al. J Cosmet Dermatol. 2013;12(1):41-48.