If metal frames cause a reaction, nickel's usually the culprit. Most metal frames are made of a nickel alloy. Other metals used include aluminum, stainless steel, titanium, zinc, copper, beryllium, gold and silver. Stainless, titanium, gold and silver are usually hypoallergenic.
Most plastic eyeglass frames are made of zyl (also called zylonite, acetate and cellulose acetate) or propionate. Other materials used in plastic frames include: polyamide, nylon, polycarbonate, carbon and Optyl (a brand of epoxy resin). Propionate, polyamide, nylon and Optyl frames are all considered hypoallergenic.