Final answer:
A chemical depilatory that utilizes a caustic alkali preparation usually contains active ingredients like calcium thioglycolate and maintains a high pH to break down keratin in hair. The process takes about 10 minutes and is followed by rinsing and pH normalization of the skin. Hair regrowth occurs since the dermal papilla is not destroyed.
Step-by-step explanation:
The type of hair removal that uses a caustic alkali preparation is known as a chemical depilatory. These hair removal creams contain active ingredients like salts of thioglycolic acid, which effectively break down the protein structures in hair, making it easy to wipe away. The key chemical reaction in this process involves thioglycolic acid breaking the disulfide bonds of cystine in the hair's keratin.
Chemical depilatories typically have about 5-6% calcium thioglycolate in a cream base, which is necessary to keep the product in place on the skin. To maintain the high pH required for hair removal, calcium or strontium hydroxide is added, creating a pH of around 12. This high pH is crucial as it allows for the efficient breakage of disulfide bonds in keratin. After the hair has disintegrated (usually taking around 10 minutes), the area is rinsed to remove the depilatory agent. Finally, conditioners are often used post-depilation to neutralize the skin's pH back to normal levels. It is important to note that this method of hair removal does not affect the dermal papilla, so the hair will regrow.