If seeing someone hurl makes you gag, too, and then launch into a puffed-cheek, double-hands-to-the-mouth, chest-heaving dance before you either toss your own cookies or scurry safely (and dryly) away, well, we owe you a compliment.

People who feel the urge to barf when witnessing another person throw up are both compassionate and highly evolved, say two medical experts on the stomach-turning topic.

“There's good news and bad news about why upchucking causes other people in the immediate vicinity to upchuck,” said Amy Morin, who teaches psychology at Kennebec Valley Community College in Fairfield, Maine and works a licensed clinical social worker.

“The good news is, if it happens to you, it means you have empathy,” Morin said. 

In human brains, scientists have discovered “mirror neurons” that cause some people to feel the same emotions as others around us. This explains why you might tear up when you see someone in the room cry.

If that sounds like you, when you see someone vomit, your brain feels empathy and causes you to actually feel that disgust with the other person, and so the food in your gut wants to come out, explained Morin, who also writes for about.com at discipline.about.com.

“The bad news is, there's not much you can do about it. If you are prone to upchucking or gagging at the site, smell, or mention of vomit, your brain is likely fairly hard wired to react by doing so,” she added.

This wretched reaction is, in fact, still laced into our brains from ancient times – as a pure survival instinct, said Dr. Jennifer Hanes, an emergency physician at Northwest Hills Surgical Hospital in Austin, Texas. 

"Humans are communal creatures, and if our ancestral brother began to vomit from spoiled food or other illness, likely we were exposed to the same pathogen as well,” said Hanes, author of "Lady in Weighting." "When one person vomits, our body begins to retch to expel the germs or poison that may be in our system, but (have) not yet reached a toxic level to cause illness on our own.

“If one member of the tribe is sick or poisoned, chances are the other members are as well so it developed as a self-preservation reflex. If it affects you, just think of yourself as highly evolved,” Hanes said, adding: she has never vomited in the ER but has witnessed the reflex with nurses and medical students.

In contrast, nurse Mary Pitman, calls on-the-job spewing her “single greatest weakness” in the emergency room.

“I have a theory on why one person hurling can turn a room into a vomitorium,” said Pitman, a Vero Beach, Fla. resident who has spent 31 years as a nurse. “Unlike my peers, for whom suctioning thick, green secretions out of someone's lungs is the ultimate stomach churner, mine is vomiting and here's why. It's a multi-sensory experience – there’s the sight, the sound, the smell and – most of all – the memory.

“Most people at some point have vomited. Seeing someone do it, and the sight of partially digested food, brings back that cascade of memories,” Pitman said. “And it's never good.” 

Dang, she had to say "cascade." 

Want more weird health news? Find The Body Odd on Facebook.

Whether you’re a victim of illness or boozy overindulgence, a suddenly watery mouth – atop of a queasy stomach – is never a sign of good things to come.

When the drool pools, you know what’s up: your stomach contents. Literally. It’s not going to look pretty. And afterward, you’re not going to feel pretty.

But salivating before vomiting runs counter to our basic understanding of slobber. Shouldn’t that oral reaction only accompany the scent, sight, promise or actual consumption of tasty morsels?

Actually, it’s all part of the same digestive chain reaction – a chemical concoction involving your mouth and your gastric juices, the fluid generated within your gut to help your body dissolve chewed food.

“The body is attempting to solve the problem of whatever is causing the nausea and (in a sense) digest it,” said Dr. Isaac Eliaz, who blends Western medicine with acupuncture and traditional Chinese medicine – an approach known as “integrative medicine.”

“Our digestive process starts in the mouth with the saliva, which is high in amylase, an important digestive enzyme that helps break down carbohydrates. So as part of the digestive process triggered by whatever may be causing the nausea, we have increased salivation,” said Eliaz, based in Sebastopol, Calif.

At the same time, nausea stimulates the vagus nerve – which runs from the brain down through the neck, relaying information about the condition of body’s organs, Eliaz said. An upset stomach also awakens the parasympathetic nervous system, which revs and runs your “rest and digest” functions, including crying and urination plus, in this case, digestion and salivation.

In short, that extra drool means your stomach and brain are chatting up a storm as you just try to hang on through that bumpy night, or that rough morning.

But we’re not here to simply explain this weird sensation. We seek to provide a tip to, perhaps, prevent you from hurling.

Check out the wisdom offered by Ken Beckstead, 48, a Las Vegas resident: “Whenever I start to salivate excessively and feel like I am going to vomit, I start spitting the excess saliva.

“Swallowing the saliva actually makes you vomit. Spitting it out until the saliva stops filling your mouth will help you not vomit,” Beckstead said.

Doctor?

“I can say that there is, indeed, an explanation to such relief,” Eliaz said. That reason, he adds, comes via his knowledge of traditional Chinese medicine.

“It is specific to a certain energetic pattern or issue that will cause nausea: what we call in traditional Chinese medicine the accumulation of phlegm and mucus in the stomach,” Eliaz said. “In this case, spitting saliva will help relieve the condition.”

So, East or West, the solution: spit and rest. Either way, though, you'll probably need a bucket. 

Related: 

Do shifty eyes really mean you're lying?

Lack of sleep won't make you nuts

Want more weird health news? Find The Body Odd on Facebook.