A synthetic rubber copolymer of acrylonitrile and butadiene used as an alternative to latex for the manufacture of surgical gloves. Butadiene adds softness and flexibility and contributes to the elasticity of the glove. Nitrile is protein-free and is therefore less likely to cause the irritation and allergic reactions sometimes experienced with latex; however, many of the chemicals used in the manufacture of nitrile gloves are the same as those used for manufacturing latex gloves, and therefore allergic contact dermatitis may still occur. Nitrile gloves are resistant to puncturing, tearing, and abrasion and are frequently coloured blue to make pin holes more visible. A high modulus of elasticity can lead to hand fatigue over time.