Yo! Monster Allergy is a card game where players try to outbid each other with the cards they have in their hands. Players take turns choosing cards from their hand. They play these cards in front of the player to their left and says a number and a color. This player can either accept these cards and play new cards in front of the player that is clockwise next to him, with the only restriction that the number must be higher. Or he can say 'YO!'. When a player shouts YO!, you look at the cards, if the player lied and played a number less than the number he called, the player loses some points. If a player has zero points he is eliminated from the game. The surviving player wins the game.