Not sure if this is true. But, my beauty consultant advised me so.
I was using Loreal whitening foam cleanser alternating with Artistry whitening cleanser and that's when my beauty consultant told me not to overuse whitening products. Could she be referring to cleanser only or other whitening products?
The reason she gave me was whitening products contain 'harsher' ingredients which function to remove or reduce pigments. Maybe, she's only cautioning me to use less whitening cleaser and not other whitening products.