Humans have all kinds of habits, from drinking a coffee after waking up each morning to watching TV in bed every night before going to sleep. But some of the unhealthiest habits are the ones that spread germs to innocent passersby. And many of those habits involve putting things in our mouths that don’t belong there.

Biting nails or fingers

Some people bite their nails — or the chew the skin around their fingernails — when they are stressed, worried or bored. But our fingernails and the sections of skin around them are saturated with germs that transfer to our mouths, and from there to our internal organs, every time we take a bite. Chewing on that area can also potentially create “cuts and abrasions that could easily pick up even more bacteria or yeast,” according to AOL Lifestyle. “You're also at a higher risk of gum disease and infection if you're a habitual nail biter.”

And if you don’t wash your hands after biting your nails and then touch another surface that other people come into contact with, you are potentially infecting all of them as well.

Not washing up in the restroom

Which leads us to washing habits in the bathroom. Feces can carry salmonella, E. coli and the norovirus and can spread certain respiratory infections, according to the Centers for Disease Control and Prevention. “A single gram of human feces — which is about the weight of a paper clip — can contain one trillion germs.”

But we don’t have to poop to wash our hands; everyone should be washing their hands after using the restroom regardless of what came out. We’re looking at you, men at urinals: The Huffington Post reports that men are more likely than women to leave the bathroom without washing their hands, especially when they were only handling their own body parts.

“Many men suggested that unless they had a bowel movement, there would be no need for washing their hands,” Michigan State University professor Carl P. Borchgrevink, who authored a study on the subject, told the Huffington Post.

Leaving the lid open

Even if we wash up, the bathroom is still a jungle. The Mythbusters have proved on their show that “every time you flush a toilet, it releases an aerosol spray of tiny tainted water droplets,” according to the Discovery Channel. If the toilet lid is left open, those tainted particles go everywhere.

That includes any innocent toothbrushes loitering nearby. Those become “speckled with microscopic fecal matter.” Actually, even the ones that had never been in the bathroom were found to have fecal matter on them, showing that it travels everywhere.

Using hands as a tissue

Another great way to spread personal germs is to sneeze or cough into your hands, as opposed to using a tissue or potentially even the inside crook of the elbow.

“When these germs get onto hands and are not washed off, they can be passed from person to person and make people sick,” the CDC warns. They can get into food that is then consumed and can even “multiply in some types of foods or drinks, under certain conditions, and make people sick. Germs from unwashed hands can be transferred to other objects, like handrails, table tops, or toys, and then transferred to another person’s hands.”

Using teeth as scissors

In addition to it being bad for your teeth, using your mouth-bones to open packages is unhygienic. Much in the same way biting your nails and sneezing into your hands spreads germs, putting a wrapper into your mouth transfers germs in both directions, making you susceptible to whatever you pick up and others susceptible to whatever you leave behind if another person touches the wrapper after you.

And if you want to keep those pearls shiny and healthy, The Independent warns that “opening a bottle, packet ... or anything else with your teeth can be extremely damaging, as [it] wears away your teeth and you are far more likely to chip a tooth.”

Chewing on a pen

Again, transfer is the huge problem to the nervous habit of chewing on pens or pencils. The pen has been touching germy hands all day — some of them maybe that were not your own. And like using your teeth to open packages, chewing on a pen could damage teeth.

There’s also the terrifying prospect that your mouth could turn into a scene from Ernest Goes to Jail.