Aging of the skin is caused by genetic factors or by external influences, according to the American Academy of Dermatology. During aging, thinning of the skin and slower production of collagen and elastic fibers cause wrinkles to develop. External factors that speed aging of skin include sun exposure, repetitive facial movements and smoking. The skin on the face and neck is especially prone to wrinkles because it receives more sun exposure than other body parts.
Read more: http://www.livestrong.com/article/276396-wrinkle-injections-for-the-neck/#ixzz1IU56CqS0