In my opinion there are few conditions which would prevent you from enjoying massage. You should not book a massage if you have a fever, cold/flu, or contagious skin infection. That's it.
There are many other conditions in which your therapist may need to adapt his/her techniques (i.e. arthritis or osteoporosis) or avoid an area completely (i.e. cuts or burns). With some conditions it is a good idea to get an approval from your physician before you receive massage (cancer, certain heart conditions, pregnancy). This doesn't mean you can't get massage. But its always better to err on the side of caution.
Your therapist can advise you about your specific needs.