Hello and welcome to healthcaremagic You seem to have developed irritation to this combination. First and foremost, this combination should never be used on the delicate skin of inner thighs as both hydroquinone as well as tretinoin have an inherent irritant potential and can cause severe irritation, discomfort and pain. I would suggest that you stop using it immediately. Rather, I would suggest that you use a moderately potent topical steroid e.g fluticasone propionate cream for a few days, for the irritation that you have already developed. Thereafter, you may use a kojic acid based cream e.g Kojic cream (2% kojic acid) which is also an effective skin lightening agent and safe even if used for an extended period of time. However, since it is a prescription product therefore I would suggest that you visit a dermatologist before trying it. Hope this helps Regards