HI THERE, THERE ARE MANY REASONS WHY A CLIENT MAY BRUISE, AND I PRESUME THAT YOU ASKED ALL RELEVANT MEDICAL QUESTIONS PRIOR TO TREATMENT. PERHAPS YOU DID NOT STRETCH THE SKIN ENOUGH, OR MAYBE THE DIRECTION THAT YOU PULLED THE STRIP WAS INCORRECT. PRACTICE DOES INDEED MAKE PERFECT! DONT GIVE UP, OFFER CLIENT THE NEXT TREATMENT FREE. GOOD LUCK, AND KEEP IN TOUCH