I am not going to lie - it is not pleasant. But just remember that us girls do it and manage it on all areas of our body - the chest would probably be one of the least painful. The amt. of time it lasts varies for everyone - the salons will tell you 4-6 weeks. But remember that all hair grows in cycles - so when you go to get waxed, there are many hairs that are just under the surface about to 'sprout' in a few days - so those hairs will be seen a few days post wax. Also - when doing such a large area like that - many hairs are not pulled out from the root - they are broken, in which case those will continue to grow also. I would say the 1st week is all smooth and from then on - you will start to feel hair again but it would be light. By 4 weeks you need to do it again.
