Most effective: Large, flat areas similar to arms and legs. Least effective: Curved areas the same as the underarms, and probably do cause significant trauma to the face as well as other thin skinned areas. Are you still in high school? If you are, look at your school district's website. https://maps.google.ae/url?q=http://www.betsyrosspatterns.com/10-signs-youve-found-a-good-hair-salon-for-your-needs/