Some people like to eat garlic, some don’t, but most of us don’t know what makes the pungent bulb repel or attract. Now scientists led by Ardem Patapoutian of The Scripps Research Institute in La Jolla, Calif., and Novartis Research Foundation in San Diego have published research in the May 24 issue of Current Biology that tells exactly how compounds in the herb activate sensory responses in the mouth.

They used a fluorometric imaging plate reader to perform calcium-imaging experiments to pinpoint allicin as the substance in cut or crushed raw garlic that trips protein thermoreceptors, causing sensations of heat or prickling. These receptors are akin to those that react to “hot” and “cold” components in chili peppers, mustard, cinnamon, wintergreen and peppermint. Cooked or roasted garlic tastes milder because heat tames the compound, converting it to less-potent sulfides.

The researchers believe that garlic evolved the allicin reaction to make it less palatable to animal foragers, although many humans have acclimated their taste buds to appreciate the stinky stuff.

It still remains to be explained why the bulbous herb, even unpeeled, produces such a negative response in vampires.