Hickeys are not dangerous to your health and cannot cause any other health issues.
The only danger from getting a hickey is that your skin will get a bruise but the bruise should go away after a week or so.
You cannot get cancer or other diseases through a hickey but you might get some bleeding and it can hurt for awhile to get a hickey.
But you won't get in any other danger from a hickey or have any other diseases but it's best to avoid getting hickeys because they can hurt and cause bruises and can cause your skin to not look good.
I used to get hickeys from my boyfriends when I was a teenager and although they hurt the bruise went away and I was okay and never had any health issues from them.