widely used. Chemical processes may be employed to reduce the amount of antigenic protein in Hevea latex, resulting in alternative natural-rubber-based materials such Vytex Natural Rubber Latex. However, non-latex gloves have not yet replaced latex gloves in surgical procedures, as gloves made of alternative materials generally do not fully match the fine control or greater sensitivity to touch available with latex surgical gloves. (High-grade isoprene gloves are the only exception to this rule, as they have the same chemical structure as natural latex rubber. However, fully artificial polyisoprene—rather than "hypoallergenic" cleaned natural latex rubber—is also the most expensive natural latex substitute available.) Other high-grade non-latex gloves, such as nitrile gloves, can cost over twice the price of their latex counterparts, a fact that has often prevented switching to these alternative materials in cost-sensitive environments, such as many hospitals. Nitrile is more resistant to tearing than natural latex, and is more resistant to many chemicals. Sulfur compounds used as accelerants to cure nitrile can speed the tarnishing process in silver, so accelerant-free nitrile or other gloves must be used when handling objects made of these metals when this is not acceptable. Double gloving Double gloving is the practice of wearing two layers of medical gloves to reduce the danger of infection from glove failure or penetration of the gloves by sharp objects during medical procedures. Surgeons double glove when operating on individuals bearing infectious agents such as HIV and hepatitis, and to better protect patients against infections possibly transmitted by the surgeon. A systematic review of the literature has shown double gloving to offer significantly more protection against inner glove perforation in surgical procedures compared to the use of a single glove layer. But it was unclear if there was better protection against infections transmitted by the surgeon. Another systematic review studied if double gloving protected the surgeon better against infections transmitted by the patient. Pooled results of 12 studies (RCTs) with 3,437 participants showed that double gloving reduced the number of perforations in inner gloves with 71% compared to single gloving. On average ten surgeons/nurses involved in 100 operations sustain 172 single gloves perforations but with double gloves only 50 inner gloves would be perforated. This is a considerable reduction of the risk. In addition, cotton gloves can be worn under the single-use gloves to reduce the amount of sweat produced when wearing these gloves for a long period of