1. Your Ear Canal

You should never stick your fingers-or anything else-in your ears. "Introducing anything into the ear canal can tear the thin skin that lines the ear canal,” says John K Niparko, MD, professor and chair of the department of otolaryngology - head & neck surgery - at the Keck School of Medicine of USC.

If you feel a persistent itching sensation in your ears, see an otolaryngologist rather than trying something DIY. "An otolaryngologist can assess the problem-whether it be wax accumulation, eczema of the skin, or infection-like swimmer's ear, for example. A tailored program of treatment, ear hygiene, and moisturising of the skin should be put into play," says Niparko.

2. Your Face

You can use your hands to wash your face or apply skincare. But otherwise, keep your paws off. When you rest your hands on a germy surface and then bring them to your forehead, it increases your likelihood of getting sick-and breaking out in spots, too. Your fingers contain oils that can plug your pores, says Men's Health dermatology adviser Adnan Nasir, MD.

3. Your Butt

Wiping and washing aside, just don't. "The anus does contain bacteria that could potentially be harmful," says Jared W. Klein MD, PhD, medical director of the after care clinic at Harborview Medical Center. After you poop or touch your butt for any other reason, wash your hands thoroughly.

4. Your Eyes

Unless you're putting in contacts or washing away a particle that found its way into your peepers, keep them off limits. You can easily introduce germs into your eyes, says Men's Health ophthalmology adviser Kimberly Cockerham, MD. Those bugs could cause anything from pinkeye to a scarier infection. Follow her simple rule: "Don't touch and don't rub." And if you do experience itchiness, dryness, or contact lens discomfort, talk to your eye doc. He or she can address the underlying issue.

5. Your Mouth

Recent research from the U.K. found that people put their fingers on or around their mouths an average of 23.6 times per hour when they were bored at work. And they still did it 6.3 times an hour when they were busy! That's a problem: In a landmark study published in the Journal of Applied Microbiology, a third to a quarter of germs tested transferred from study subjects' fingers to their mouths. Maybe you should think about stealing your kid's pacifier.

6. The inside of Your Nose

Quit digging for gold: In a 2006 study of ear, nose, and throat patients published in the journal Infection Control and Hospital Epidemiology, nose pickers were 51% more likely to carry Staphylococcus aureus bacteria in their schnozzes than those who kept their hands off.

7. The Skin under Your Nails

Lots of nasty bacteria, including staph, can live there. "Your nails should be short to reduce the chances of bacterial carriage, and such nails only need a gentle nail brush to remove debris and often," says David De Berker, MRCP, consultant dermatologist at the British Dermatology Center.

"Picking tends to create trauma in its own right," he says, "and then any bacteria or yeast can cause further problems-sometimes resulting in a pattern called onycholysis, where the nail lifts off the nail bed."

Which of these surprised you the most about what body parts you should never touch? Are you way more cautious now? Tell us in the comments below!