Costumes allowed people to lose their inhibitions and let their hair down. Worktime was turned into playtime. Beltane is also a fire festival. Farm animals would be driven through the embers of fires which were sometimes kept burning for days. This was thought to purify them and protect them against disease.
People also run or jump over the embers.
This comes from ancient times when there would be a human or animal sacrifice to ensure a fertile year to come. From Beltane animal sacrifices, when it was deemed an honour to wear the head and hide of one the slaughtered animals, comes the tradition of hobby horses. These can still be seen in many places in Britain on May Day. The luckiest day to be handfasted is Beltane, followed by Samhain. Couples would often jump backwards over the fire at the end of the ceremony.