Warning: massage rant follows!!!
I am a highly qualified aromatherapist/massage therapist (trained at the Tisserand Institute) and work as a mentor to trainee therapists currently studying at Neals Yard Remedies.
I would never refuse to treat someone who had either their period or cancer. It is an outdated view that massage can spread cancer cells. However, it is useful to know this information since it does affect which oils I would use, which areas to avoid (because of potential for sore treatment sites), the depth of massage etc. Also because aromatherapy and massage should be holistic and therefore you may well instigate a psychological reaction to the oils and the hands on work which needs to be considered before deciding on blend and treatment plan.
As for not treating someone with their period - absolute tosh. There are oils which have hormonal balancing qualities and some which are uterine relaxants. It isn't going to make you bleed more it will simply speed things up (as massage generally gets all body systems working more effectively).
I am curious to know which essential oils promote excessive bleeding as I have never heard this before. True, some oils are believed to have abortifacient qualities in high doses. Some are incredibly toxic and imo should not be sold as over the counter remedies. What makes me laugh is that there is a general consensus that lavender is a "safe" oil but there are many different types and species and not all of them are safe for pregnancy or children for example. That's why we spend 2 years studying botany, chemistry, biology and anatomy & physiology so that we do know what is safe to use and when.
Many of the hormonal oils are incredibly beneficial before and during your period (and also at other times in the cycle). If you want to see a good therapist, contact IFPA and they will give you a list of qualified therapists in your area.
Rant over