If human fingernails tasted like pepperoni pizza, biting them would be understandable.

But in the real world, fingernail biting is an unhygienic, hard-to-quit habit. And it’s tied to the spectrum of human emotion.

We bite our nails:

In anticipation — We bite while waiting for a courtroom verdict. Or when the movie killer is about to get our hero. Or when the bases are loaded with two outs in the bottom of the ninth.

Out of boredom — We bite when that history teacher won’t shut up. Or when that certain co-worker goes on and on about his dog or her cat for the umpteenth time.

In anger — We bite when we can’t fight.

Most often, however, we bite our nails for the same reason Tulare resident Matthew Boyett does: stress.

“School work does it a lot,” says Boyett, a 19-year-old student at California State University, Fresno.

The U.S. National Library of Medicine defines fingernail biting as a sign of anxiety, chronic tension or uncontrollable compulsion that, in extreme cases, requires psychological help.

Dolores Carbajal, 35, often notices her two boys — ages 7 and 9 — chewing on their fingernails when they’re bored or uncomfortable.

“But then when I’m deep in thought about something, I catch myself [doing it],” says Carbajal, an Exeter resident. “I know I’ve been doing it since I was their age, so I worry about them.”

Carbajal can’t recall any health problems directly related to fingernail biting. But, she speculates, it might have led to more than one bout with a cold or flu.

Let the experts chew on that one.

“Fingernails are the dirtiest part of the hand,” says Melissa Janes, direction of education and infection control at Tulare District Hospital. “All kinds of nasty things are under there.”

Often, germs are spread when sick people touch their face and then fail to wash their hands thoroughly.

Biting the nails ups the germ count considerably.

Also, doctors say, severe nail biting can expose underlying tissues to infection.

But even though we know where our fingers have been — in public restrooms, on the dog, under the couch cushions digging for the lost remote — we still bite our fingernails.

Part of the problem is that there is no recognized handbook — pun intended — on how to stop biting your nails. Thus, parents have a tried a variety of tricks over the years.

Among them:

The They’ll-Grow-Out-of-It Solution — You may want to find an alternative, especially if your child’s fingertips or cuticles bleed and become infected, which does happen.

The Distraction Solution — Many children bite because they’re bored, as during long car rides. So parents find something — from coloring books to books to video games — to keep their children’s hands occupied.

The Scare-’Em-Straight Solution — You may have heard that, if you bite your nails too much, a disgusting lump of old nails will form in your stomach and rip your guts apart. Yep, Stephen King has nothing on grandma.

The Fingernail-Polish Solution — For girls, nice-looking nails that have been polished and manicured can prevent biting.

The Chili-Powder Solution — Sprinkle a little chili powder on the fingertips or dip the hand into a little jalapeño juice. This plan may backfire for Mexican-food lovers, however.

There’s also this approach: Teach children about germs and how they operate.

“If they’re educated and know what can be under their fingernails,” Janes says, “you’d think they would stop on their own.”

But old habits die hard. What would it take for Boyett to stop biting his fingernails?

“I don’t know,” he says, “maybe another limb to chew on.”

My mother tried putting that chile mixture on my hands and look where it got me!