The NFL is banning the use of smelling salts and ammonia packets before and during all games, a ruling that has upset 49ers TE George Kittle.

Ammonia and smelling salts have long been used as a stimulant by NFL players as well as other athletes, though the risks that come with their use have been noted. Many boxing competitions, for instance, have banned smelling salts under the pretense that their use can mask serious injury.