As annoying  COUGH  and embarrassing as it seems,  COUGH COUGH  especially in public settings like buses and audi  COUGH GASP  toriums, pardon me, I just need a second, HACK HACK HACK, whew, that’s better it’s actually a good thing to  COUGH. Um, sorry.

Whether a cacophony of dry, seal-like barks or a rumble of marshy eruptions, coughing is “really quite protective,” said Dr. Berrilyn J. Ferguson, an ears, nose and throat specialist at the University of Pittsburgh Medical Center.

“You’re trying to keep the airway and the lungs clear of this thick mucus that can have this bacteria or viruses in it,” she explained.

Sneezes, too, are protective, blowing undesirables like viral particles out of the body.

If you’re ever wondered why we do what we do when we’ve got a cold or the flu, here’s a primer.

Often, colds start with a sore throat and sneezing.

The sneeze reflex is triggered by irritation of sensory nerves in the nose, which signals the brain. After a big inhale, the vocal cords close, muscles contract and thoracic pressure builds. The soft palate and uvula are depressed so the expelled air flows not only through the mouth, but also forcefully through the nose.

“It’s like a hurricane,” Ferguson marveled. “It’s really, really powerful.”

The highest sneeze speed recorded is a blustery 103 miles per hour.

Some people have a photic sneeze reflex, meaning that when they enter bright light after being in a darkened room, they sneeze. Also known as the solar sneeze reflex and ACHOO syndrome, the reflex is thought to begin in the brain itself, rather than at the nose.

A cough starts when an airway irritant, like smoke, fumes or a foreign body, stimulates sensory nerve receptors in the throat or lungs, and a message is sent to the brain.

The brain instantly fires back nerve impulses that make us take a deep breath, just like with a sneeze. The vocal cords squeeze together, the diaphragm relaxes and the muscles of the rib cage and abdomen tighten, all of which builds pressure in the thorax.

But unlike during a sneeze, the positions of the soft palate and uvula don’t change. When the cords pop open, foreign particles and mucus are expelled solely through the mouth.

“That’s called a productive cough,” Ferguson said. “A lot of times as the illness goes along, things get drier and you no longer bring anything up with it. Then it’s called a non-productive cough.”

Occasionally, persistent coughing causes vocal cord irritation that leads to more coughing, the doctor noted. Treatment with strong cough suppressants may be needed to break that cycle.

“If people have a really bad cough, then we prescribe things that are narcotic to really suppress the cough reflex,” Ferguson said. “But most of the stuff you get over the counter is about as good as the stuff we’re prescribing.”

Productive coughs may be treated with expectorants, such as guaifenesen, which thin mucus and make it easier to expel. Non-prescription remedies for dry, irritating coughs usually include dextromethorphan.

A new cold medication that is scheduled to be reviewed this spring by the Food and Drug Administration is generating excitement because studies show it reduces the length and severity of the common cold caused by rhinoviruses.

When taken within a day or two of symptom onset, the drug pleconaril attacks the cold virus itself, rather than just the symptoms.

About half of all colds are caused by rhinovirus strains, said Dr. Deborah Gentile, an allergy specialist and researcher at Children’s Hospital in Pittsburgh. Adenoviruses, coxsackieviruses and many others can also cause respiratory illness.

“There’s nothing that can target all the different viruses,” the researcher said. But “there are actually newer antihistamines coming out that might have some benefit in a cold.”

Gentile and her colleagues have found that histamine, the body chemical that is elevated in allergy, is also up during colds.

Pediatric studies of pleconaril are under way. If approved by the FDA, it would be sold by prescription under the brand name Picovir.