Some of the most common causes of bad breath are the most obvious ones. You know it's time to brush when you've had some particularly garlicky shrimp scampi or you practically breathe fire first thing in the morning.

But there are some surprising causes of bad breath, known to science-y types as halitosis, the product of odor-causing bacteria buildup in your mouth and between your teeth (gross, we know).

Here are some of those sneaky culprits. Makes us want to brush just thinking about it...

  • 1
    Medications
    It's not that your Rx is causing a stink, but meds carry with them dry mouth as a side effect. Saliva is essential to washing odor-producing particles free, so when there's less of it, odor increases. It's essentially the same reason you get morning breath, according to the Mayo Clinic.
  • 2
    Respiratory Tract Infections
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    A bout of bronchitis or even a cold might be the cause of that stench. According to a 2006 report, respiratory tract infections cause bad breath thanks to "nasal or sinus secretions" passing into the throat and mouth. Bronchitis, pneumonia, sinus infections and postnasal drip can all lead to bad breath, WebMD reports.
  • 3
    Mouth Breathing
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    So you're a mouth breather. Aside from your propensity to drool while you're sleeping, you might find yourself with stinkier than average breath upon waking. That's because, just like with certain medications, breathing through the mouth cuts down on saliva, leading to a drier, smellier mouth.
  • 4
    Obesity
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    A 2007 study found that obese people were more likely to have bad breath, but a 2013 study took that link a step further. It turns out that organisms that live in the gut of obese people may give off a certain, distinctive gas, causing bad breath in the mouths of the overweight. The specific microbe in question is present in about 70 percent of people, but higher in about 30 percent, possibly predisposing those folks to obesity, Time.com reported.
  • 5
    Skimping On Carbs
    Atkins Diet fans will recognize the word "ketosis". This fat-burning process occurs when the body turns to fats and proteins for energy, since carbs aren't available, Kenneth Burrell, DDS, told WebMD. In this state, however, the body releases certain chemicals into the breath that cause odor -- and this isn't a stink you can brush away, he said. "All the brushing, flossing and scraping of the tongue that you can do is not possibly enough to overcome this." Everything in moderation, even carbs.
  • 6
    Underlying Medical Conditions
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    It might not be the typical "bad" breath you're used to; rather a "potent" fishy smell could signal kidney problems, and whiffs of fruit could be a sign of uncontrolled diabetes, US News reported. Certain cancers produce chemicals in the body that may in turn lead to "distinctive breath odor," according to the Mayo Clinic, and chronic heartburn may also contribute to bad breath, since stomach acid is constantly refluxing.

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  • Bar Of Soap

    Despite the pervasive attitude that a bar of soap somehow cleans itself, the <a href="http://www.cdc.gov/mrsa/groups/advice-for-athletes.html" target="_blank">CDC recommends liquid soap over a bar</a> when possible to cut down on sharing. A 1988 study found that germy soap <a href="http://www.ncbi.nlm.nih.gov/pubmed/3402545" target="_blank">isn't likely to transfer bacteria</a>, but a 2006 study refuted that idea, citing <a href="http://www.outsideonline.com/fitness/fitness-coach/How-Clean-Is-Soap.html" target="_blank">soap as a source of continuous reinfection in dental clinics</a>, Outside magazine reported. It could be because bars of soap don't usually dry all the way between uses, says Schultz, especially on the bottom, leading to an accumulation of bacteria, fungi and yeast that can be passed from person to person, he says.

  • Hats, Helmets, Hairbrushes And Combs

    Headwear is an obvious culprit when it comes to the <a href="http://www.cdc.gov/parasites/lice/head/gen_info/faqs.html#transmit" target="_blank">spread of head lice</a>, but so is making contact with sheets or pillows or couch cushions that have recently been used with an infested person, according to the CDC.

  • Antiperspirant

    There are two types of sweat, and one is smellier than the other. The odor comes from <a href="http://www.huffingtonpost.com/2013/08/06/facts-about-sweat_n_3709248.html" target="_blank">bacteria that break down the sweat on your skin</a>. Deodorant, therefore, has certain antibacterial properties to stop the stink before it starts, explains Schultz. Antiperspirants, on the other hand, "are only interested in decreasing perspiration," he says, so they don't contain the same germ-killing powers. If you share a roll-on antiperspirant, you could transfer germs, bacteria, fungi and yeast from person to person, he says. Stop sharing, or switch to a spray. Even with a deodorant stick, he says, you can transfer skin cells and hair, which plays to some people's lower threshold for the gross, but won't result in infection, he says.

  • Nail Clippers, Buffers And Files

    You <a href="http://www.today.com/id/24712504/ns/today-today_health/t/hidden-dangers-beauty-salon/#.UjnPkGQ4WH4" target="_blank">wouldn't share 'em at a salon</a> -- so don't share them with pals, either. If cuticles are cut or pushed back too far, or callused skin is removed, you could have little cuts in your skin, perfect openings for bacteria, fungus, yeast and viruses to be exchanged from tools that haven't been properly sanitized between users, according to the Today Show. Hepatitis C, staph infections and warts can all be spread this way.

  • Makeup

    Keep your mascara wands and lipstick tubes to yourself if your friend who wants a swipe has an <a href="http://www.webmd.com/beauty/makeup/dirty-secret-do-you-share-makeup" target="_blank">obvious infection, like pinkeye or a cold sore</a>. But Schultz says that on a case-by-case basis, <a href="http://www.dermtv.com/it-safe-wear-your-friends-makeup" target="_blank">makeup may actually be safe to share</a>. That's because most cosmetics have a number of preservatives on the labels, which are designed to kill bacteria and other growths in products made with water, thereby cutting down on infections.

  • Razors

    It probably goes without saying, but you should never share anything that could exchange blood. "Avoid sharing anything that might have contact with blood, even if there's no apparent blood," says Tosh. Since shaving can result in <a href="http://www.doctoroz.com/videos/spreading-disease-things-you-should-never-share" target="_blank">tiny nicks in the skin</a>, viruses and bacteria left behind on razors can enter swiftly into the blood, according to "The Dr. Oz Show", and blood-transmitted viruses like hepatitis B are "unbelievably transmissible," says Tosh.

  • Drinks

    Sharing a water bottle or a cup can lead to saliva swapping -- and not in a good way. The <a href="http://www.huffingtonpost.com/thomas-p-connelly-dds/sharing-drinks-healthy_b_3241147.html" target="_blank">germs that cause strep throat, colds, herpes, mono, mumps and even meningitis</a> can all be exchanged with a seemingly-harmless sip, dentist Thomas P. Connelly writes. However, Tosh points out that while many people carry the virus that causes cold sores, some won't ever actually have one. "Should you <em>never</em> share a soda?" he says, incredulously. "Usually, it's not going to cause problems."

  • Toothbrushes

    Sharing is a no-no, according to the CDC, since you could <a href="http://www.cdc.gov/oralhealth/infectioncontrol/factsheets/toothbrushes.htm" target="_blank">pass infections along on those bristles</a>, especially if, say from flossing, there is any small amount of bleeding, says Schultz.

  • Earrings

    When you poke an earring through your ear, you may make a little break in the skin, <a href="http://www.doctoroz.com/videos/spreading-disease-things-you-should-never-share" target="_blank">allowing viruses from the last wearer to enter the blood</a>, according to "The Dr. Oz Show". Tosh points out that most people inserting earrings won't be drawing blood, but there is still potential risk if you don't clean your jewelry between wearers.

  • Earphones

    We know you love your jams, but frequent earphone use seems to <a href="http://www.ojhas.org/issue26/2008-2-4.htm" target="_blank">up the amount of bacteria in your ears</a>, according to a 2008 study. That bacteria could spread to another's ear if you share headphones, and could lead to ear infections. Avoid sharing -- or at least wash 'em first -- which, by the way, <a href="http://www.geeksugar.com/How--Properly-Clean-Your-Earbuds-7686915" target="_blank">you should probably do more frequently anyway</a>! Even over-the-ear headphones could pass along lice, says Schultz