Hydroquinone can be applied while having an IPL treatment. Make sure it is applied in the evening and usesunscreen in the daytime.
Hydroquinone and IPL are often used in combination. HQ should be applied nightly to dark areas, and you need to be using a good sunscreen daily. "This answer has been solicited without seeing this patient and cannot be held as true medical advice, but only opinion. Seek in-person treatment with a trained medical professional for appropriate care."