I thought I would look up garlic and when I read this I just had to post it:
Garlic has been regarded as a force for both good and evil. A Christian myth considers that after Satan left the Garden of Eden, garlic arose in his left footprint, and onion in the right. In Europe, many cultures have used garlic for protection or white magic, perhaps owing to its reputation as a potent preventative medicine. Central European folk beliefs considered garlic a powerful ward against demons, werewolves, and vampires. To ward off vampires, garlic could be worn, hung in windows or rubbed on chimneys and keyholes.
The association of garlic to evil spirits may be based on the antibacterial, antiparasitic value of garlic, which could prevent infections that lead to delusions, and other related mental illness symptoms.