Can topical hydroquinone cause ill side effects like headaches or anything like that?

I was looking at the cosmetics database for a listing of toxic ingredients today and hydroquinone got a hazard rating of the highest which was a 10! Whereas kojic acid got a hazard rating of 1? I think I'll be sticking to the kojic acid.

I got hq and had no bad side effects... headaches? I don't think so, but anyway go to a doctor