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It's allergy season again, so there's a lot of sneezing going around.

Sneezing can be caused by crazy things like being too full, seeing a bright light, or even orgasm. For how common sneezing is — other animals sneeze too — scientists actually know very little about the phenomenon.

In most cases, "a sneeze is designed to expel foreign particles and irritants from your airway, particularly your nasal cavity, and is a protective reflex, said Dr. Jonathan Moss of Charlotte Eye Ear Nose & Throat Associates, in an email.

And what comes after a sneeze? In the US it's traditionally a "bless you."

"The Greeks and Romans took sneezing as a sign of wellness and expressed their good wishes to the person who sneezed using the phrase 'live long,' or 'May Jupiter bless you,'" according to a Turkish scientific review of sneezing and itching published last year in Nasal Physiology and Pathophysiology of Nasal Disorders.

But somewhere along the way, sneezing fell out of good graces.

In the 14th century Pope Gregory VII asked that 'God Bless You,' become "a short prayer to be said after every sneeze to protect against the plague," said the authors in the review.

Another potential response? The German word "Gesundheit," which means "health."

According to this amazing Wikipedia page of "Sneezing Responses" around the world, many countries around the world reference health and longevity in their sneezing responses, only some referring to God.

Leslie Baehr contributed to this post.