<P> Helmet - to - helmet collisions are occurrences in American football when two players' helmets make head - to - head contact with a high degree of force . Intentionally causing a helmet - to - helmet collision is banned in most, if not all, football leagues . </P> <P> Despite its long association with American football, this type of contact is now considered to be dangerous play by league authorities due to the potential of causing serious injury . Major football leagues, such as the National Football League (NFL), and NCAA, have taken a tougher stance on helmet - to - helmet collisions after the US Congress launched an investigation into the effects repeated concussions have on football players and the new discoveries of chronic traumatic encephalopathy (CTE). Other possible injuries include head traumas, spinal cord injuries, and even death; nevertheless helmet manufacturers are constantly improving their designs in order to best protect their users against injuries from such collisions . </P> <P> The crackdown on helmet - to - helmet collisions has resulted in reappraisals of the sport . An image of two helmets smashing together--which had been a staple for 20 years--was dropped in 2006 from Monday Night Football on ESPN . The NFL also ordered Toyota Motor Company to stop using a similar helmet collision in its advertisements . </P>

When did the helmet to helmet rule start