An etiquette expert has weighed in a common birthday tradition that has become controversial for spreading a slew of germs.

Germs — like viruses, bacteria, and fungus — respond differently to cold and hot temperatures. For example, the flu virus thrives in colder weather, which is why flu season is in the winter.

Afterward, the document says the student asked Woods for a hug, but she refused and told him, “You have nasty germs ... was within a foot of him and spraying the chemicals directly at ...