Which of the following is a common allergen in nail products?

Formaldehyde is recognized as a common allergen in nail products, particularly in nail hardeners, adhesives, and some types of nail polish. This chemical has the potential to cause allergic reactions in susceptible individuals, leading to symptoms such as redness, itching, and inflammation of the skin.

The reason formaldehyde is prominent among allergens in this context is due to its use as a preservative and its ability to release gases that can affect individuals who are sensitive to it, resulting in contact dermatitis.

Other choices, while they may cause irritation, are not typically categorized as allergens. Acetone is primarily known as a solvent for removing nail polish and is widely tolerated, although it can be drying. Alcohol is frequently used as a disinfectant but generally does not provoke allergic reactions. Glycerin is often used as a moisturizer and is typically non-irritating and safe for most skin types. Thus, formaldehyde stands out due to its specific allergenic properties in the realm of nail care products.