The NFL sent a memo to teams Tuesday banning all forms of ammonia inhalants and smelling salts from games, pregame activities and halftime, following an FDA warning about their unproven safety and efficacy.

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.

The NFL is banning the use of smelling salts during games, citing safety concerns and the potential to mask concussion symptoms.