My daughter is a supplier of Candylipz in the UK and has sold thousands and the feedback is really positive They are a great product and a good alternative if you don't want fillers.
They can bruise and she warns everyone about this on the website,but generally most bruising is slight if you have followed instruction.
There is a conditioning period of about 7 to 10 days to follow where you build up use,after which time you will not bruise again at all.If people carry on bruising or suffer dramatic bruising its possible they are anaemic.
You can plump your lips up as much or as little as you like and the effects can last from 1 to 4 hours.They have been in the states a lot longer than here and been thoroughly tested and passed safe.There is lots of info and videos online if you do a search and reviews are good.
Its like anything else if you don't follow instructions then you may well get a bad outcome.If you want more info PM me and I will point you in the right direction