Tanning question, pic attached

[Louise322]

Anyone know why this little crease on my arm never changes colour?

I go a deep brown in the sun but I've caught a bit of sun recently and noticed that little part never tans on either arm! I've noticed it's the same for everyone if you look closely enough m

Maybe because your arm is bent more than straight? Or sweat stops you getting tanned there?

My daughter has a patch on her leg that stays white too...