Hickies are a discoloration of the skin caused by sucking or by a hard hit, the latter commonly being called a bruise. This will cause you some discomfort since bristles will be scraping against your skin. Be sure can hickey be cancerous? Source:http://www.ehow.com/how_2322136_remove-hickies.html
Not medical advice. The answer is an emphatic NO! Hickies can not cause cancer. It’s a myth. Text us!
They do becaus alot of the time they are ahving sex and they are making it more fun. If the parent does hide it from you in the beggining and say it is just a popped pimpil and have a band-aid over it they had sex Source:http://wiki.answers.com/Q/Why_do_people_give_hicki's