There are definitely a few “have to have’s”, but quite a lot depends on where you are going and what you will be doing while you are on holiday? Are you going somewhere very hot and dry? Or will it be very humid where you are going? Or are you having a snowy, winter holiday? I would say at the VERY least, a good hydrating serum (if you are not visiting the tropics or anywhere that is very humid, otherwise a very good anti-oxidant serum would be preferable), a sunblock and an excellent skin care supplement. So I would highly recommend something like Lamelle’s HA Plus serum, Heliocare SPF 50 and a powerful skin care supplement like Ovelle. If you are going to go out a lot and you intend to wear loads of make-up, then it is also a good idea to pack in a good cleanser (something like Lamelle’s gentle cleanser that also at least gives your skin a lot of “recover” benefits on top of its cleansing function).