William Chui's list of common whitening ingredients

Alpha hydroxy acids (AHAs)

Uses: Moisturises, removes dead skin cells and improves the appearance of photo-aged or pigmented skin.

Side effects: Alpha hydroxyl acids are generally well tolerated when used in concentrations of less than 10 per cent, but can increase sensitivity to the sun and ultraviolet light. Long-term use might increase the risk of skin cancer. Adverse reactions including blistering and burning have occurred.

Observations: Protection from the sun with sunscreen and clothing is recommended.

Azelaic acid

Uses: Treats rosacea and has mild lightening effects.