What is NOT a brightening ingredient?

The correct choice highlights that hydroquinone is indeed a brightening ingredient often used to lighten skin pigmentation and even out skin tone. It works by inhibiting melanin production in the skin, making it effective for conditions like hyperpigmentation, age spots, and melasma.

On the other hand, bearberry extract, magnesium ascorbyl phosphate, and asafetida serve different roles in skincare. Bearberry extract contains arbutin, which also has skin-brightening properties. Magnesium ascorbyl phosphate is a stable form of vitamin C, known for its antioxidant properties and ability to brighten the skin. Asafetida, while used in traditional remedies, does not have established efficacy as a brightening agent in skincare.

Understanding the roles of these ingredients helps clarify why hydroquinone is included in the category of brightening agents while the other options do not fit in that specific role.