Some people have allergies to the metal used in eyeglass frames. These are usually frames containing nickel. The temples become pitted, rough and green and the skin touching the frame can become quite irritated. You can prevent this problem by getting frames made of pure titanium. Titanium will never react with your skin or cause any allergies. It is also a very strong and light metal. Stainless steel frames are also available, and they rarely cause allergies. And of course, plastic frames preclude this problem.