Mouth pipetting is the practice of using suction from your mouth to draw liquid into a glass tube (called a pipette) for measuring and transferring in a laboratory. The technique works exactly the way drinking through a straw does: you place your lips on the top end of the pipette, dip the bottom into a liquid, and inhale gently to pull the fluid up to a precise graduation mark. For most of the 20th century, this was the standard method for handling everything from bacterial cultures to radioactive isotopes. It is now banned or strictly prohibited in laboratories worldwide.
How the Technique Worked
A pipette is a narrow glass or plastic tube, often graduated with volume markings along its length. To transfer a specific amount of liquid, a lab worker would place the open top of the tube against their lips, submerge the other end into the solution, and create suction by inhaling. Once the liquid rose to the correct mark, the worker would quickly seal the top with their tongue or finger to hold the column in place, then release it into a receiving container.
The method was popular because it gave experienced technicians fine control over small volumes, and for decades there was simply no affordable alternative. Mechanical pipetting devices existed in concept as early as 1915, when a researcher named Paneth recommended using a rubber balloon to avoid mouth contact, but the suggestion was not widely adopted. Mechanical and electronic pipettes only became common fixtures in labs starting in the 1980s and 1990s.
Why It Was So Dangerous
The core problem is obvious: your mouth is separated from a potentially lethal substance by nothing more than a column of air inside a thin tube. A momentary lapse in suction control, a surprise cough, or a crack in the glass could send the liquid straight into your mouth, throat, or lungs. Even without direct ingestion, the act of drawing liquid upward generates tiny aerosol droplets at the top of the pipette, exposing the user to whatever is in the solution through inhalation or contact with mucous membranes.
Labs routinely pipetted infectious bacterial cultures, corrosive acids, organic solvents, and radioactive solutions this way. The risks fell into two broad categories.
Infectious Disease
The earliest documented laboratory-acquired infection from mouth pipetting dates to 1898, when a lab worker contracted diphtheria after pipetting a culture of the bacterium that causes it. Typhoid fever became a recurring problem. A survey covering the years 1885 to 1915 identified 50 cases of lab-acquired typhoid, six of them fatal, with mouth pipetting as one of the primary transmission routes. A follow-up report in 1929 catalogued 83 additional infections, 59 of them typhoid, and again found mouth pipetting to be the most common way the bacteria reached lab workers.
These were not obscure or unusual pathogens. Any lab culturing bacteria, viruses, or parasites put its workers at direct risk every time they drew a sample by mouth.
Chemical Exposure
Accidentally swallowing or aspirating a chemical solvent can cause corrosive injury to the lining of the mouth, throat, and digestive tract. Cases of oral methylene chloride poisoning, for example, have presented with central nervous system depression, corrosive gastrointestinal damage, and in severe instances, kidney failure, liver failure, and acute pancreatitis. Acids, bases, and organic solvents all posed similar threats. Even a tiny amount of the wrong substance reaching the soft tissue inside the mouth could cause burns or systemic toxicity.
How Long Labs Kept Doing It
One of the more striking details in the history of lab safety is how long mouth pipetting persisted after people knew it was dangerous. The hazard was formally recognized as far back as 1915, and rubber bulb alternatives were recommended around the same time. Yet adoption was painfully slow. A survey in the 1960s found that 62% of laboratories were still mouth pipetting. By 1977, that number had not improved.
The reasons were part habit, part economics, and part institutional inertia. Mechanical pipetting devices were expensive and sometimes seen as clumsy compared to the fine control a trained technician could achieve with their mouth. Many senior scientists had learned the technique as students and simply passed it along to the next generation without question.
When It Was Officially Banned
In the United States, mouth pipetting of blood and other potentially infectious materials was formally prohibited under OSHA’s Bloodborne Pathogens Standard, which took effect on July 6, 1992. The regulation (29 CFR 1910.1030) states explicitly that “mouth pipetting/suctioning of blood or other potentially infectious materials is prohibited.”
The World Health Organization’s Laboratory Biosafety Manual takes an even broader position: “Mouth pipetting must be strictly prohibited. No materials should be placed in the mouth.” This applies to all laboratory substances, not just infectious ones. Most national biosafety guidelines around the world now mirror this language.
What Replaced It
Modern labs use a range of mechanical and electronic devices that eliminate any oral contact with laboratory materials. The simplest replacement is a rubber bulb or pipette pump that attaches to the top of a glass pipette. You squeeze the bulb to create suction, controlling the draw with your hand instead of your lungs.
Beyond that, several more advanced options are now standard. Electronic pipettes are lightweight handheld devices that use a motor to draw and dispense precise volumes at the push of a button. They promote better hand posture and eliminate the repetitive thumb force that older mechanical pipettes required. Repetitive pipettes can dispense the same volume over and over with minimal refills, using a finger-operated trigger. Latchmode pipettes use a magnetic assist so the user doesn’t need to hold their thumb down continuously. For high-throughput labs processing hundreds or thousands of samples, fully automated liquid-handling systems can be programmed to perform pipetting tasks without any human hand involvement at all.
These tools are now affordable, widely available, and far more precise than mouth pipetting ever was. The transition took decades longer than it should have, but the era of putting your lips on a laboratory pipette is, by regulation and common sense, over.