I have these too and have tried everything. Lancombe have a brillliant pen product which has worked on loads of people- not me.
I also thought this was to do with the sun, as I grew up at the seaside.
however I since got referred to a specialist and was told thst its hormones - the only evidence of my age!!!! They might even go later, however no sign of that.
They have given me various creams and they havent worked, next step is to check lasers. Although I already know the lasers can only work temporarily and marks caused by sun come back straight away if you go out in the sun.
Be wary of what creams you try and if they dont work then ask for a refferal to a specialist, the creams they have are better.
On a plus note Bobbi Brown do a really good corrector to cover them and a separate concealer.
good luck