U.S. Patent & Trademark Office (USPTO)
The USPTO reviews and grants patents and trademarks to individuals and companies creating and marketing hair removal products. Eventually, I will do some extensive patent analysis on this site, but for now I’ll direct you to the best places for doing your own research.
The 
USPTO website has searchable databases of hair removal patents and trademarks:
I also recommend the Delphion Intellectual Property Database as a very useful resource, although they announced in April 2001 that many services that were formerly free will become available for subscribers only.