There are a few erotic massage studios in Hamburg, but they are probably being pushed back by brothels and FKK sauna clubs, which offer so much more than just a massage.
Rue Ciel (http://winterhude.rueciel.de/) at Himmelstraße 44 is an alright place with good service and so is Felicitas Wellness (http://www.felicitas-wellness.de/), located at Borgfelder Allee 3. Both are great places to relax alongside a professional masseuse from Asia or Eastern Europe for €50 per hour.