Why You Must Never Eat, Drink or Mouth-Pipet in the Lab

Summary
In a lab, anything that reaches your mouth can carry invisible chemical or biological contamination. Eating and drinking in the lab, or pipetting by mouth, turns that invisible risk into a direct exposure. Modern lab safety rules ban food and drink in experimental areas, forbid mouth pipetting, and require thorough handwashing before you leave the lab or touch food. Second-hand and returned glassware also demand extra care: treat them as potentially contaminated until they are properly cleaned.

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1. How chemicals reach your mouth in a lab

When people think about chemical exposure, they often focus on spills or fumes. But one of the most straightforward and dangerous routes is ingestion – chemicals entering through your mouth and digestive tract.

In a lab, this can happen in several ways:

• Tasting or “checking by mouth”
  Historically, some chemists really did taste small amounts of substances to identify them. Today, this is recognised as unnecessary and unsafe.
• Mouth pipetting
  Drawing liquids into a pipette by sucking with your mouth can send the liquid, aerosols or vapour directly into your mouth or throat if you misjudge the volume or lose control.
• Contaminated hands touching food, drinks or your face
  You handle glassware, reagents, second-hand or returned items, and then:
  • eat a snack,
  • drink water or coffee,
  • touch your lips or wipe your mouth
    without washing your hands thoroughly.
• Food and drink stored or opened in the lab
  Even if you never “taste chemicals”, food and drink left on lab benches can be contaminated by splashes, vapour, dust or dirty gloves.

The common pattern is simple: any object that lives in the lab environment can carry residues you cannot see.

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2. Why labs ban food and drink completely

Most lab safety manuals include a strict rule: no eating, no drinking, no food storage in laboratories. This is not about being strict or unfriendly; it is about breaking the most direct path for ingestion.

2.1 Invisible residues are everywhere

In a lab, many surfaces can carry small amounts of chemicals:

• The benchtop where you work
• Glassware, even if it “looks clean”
• Pipettes, clamps, racks and instruments
• Your notebook, pens and keyboard if you touch them with contaminated gloves

These residues can be:

• Organic solvents
• Corrosive or irritant reagents
• Heavy metals or other toxic compounds
• Biological materials in some labs

You cannot see or smell most of these in the small amounts that matter for chronic exposure.

2.2 A real-world lesson: eating after handling glassware

In one glass factory, a worker was asked to check returned glassware that a customer had sent back. He handled the glass instruments with bare hands to inspect them, without knowing exactly what they had been used for or what residues might be present.

After the inspection, he did not wash his hands. He then picked up food and ate. Shortly afterwards, he developed signs of poisoning and later died.

We do not need the exact chemical identity to understand the chain of events:

1. Returned or second-hand glassware may have unknown residues on the surface.
2. Handling them with bare hands transfers residue to the skin.
3. Eating without washing hands transfers residue from skin to mouth.

This kind of tragedy is not dramatic or exotic. It is a series of small, very ordinary decisions:

• “I’m just touching glass, not chemicals.”
• “I’ll eat first, wash my hands later.”

The rule “no eating or drinking in the lab, always wash hands before food” exists to break this chain.

2.3 Practical rule

Because of these risks, a safe lab policy is:

• No food, drink, chewing gum or smoking in experimental areas.
• No storage of food or drink in lab fridges, freezers or cabinets.
• Eat and drink only outside the lab, after washing your hands thoroughly with soap and water.

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3. Why mouth pipetting is completely banned

Mouth pipetting once was common in chemistry and biology labs. Today, it is recognised as a completely unacceptable practice.

3.1 What goes wrong when you pipet by mouth

When you suck on a pipette:

• The liquid is very close to your mouth.
• If you misjudge the suction or the liquid “jumps”, it can enter your mouth or throat.
• Even if you spit it out quickly, your lips and mucous membranes have already been exposed.

In some cases, droplets or aerosols may enter your airway before you even notice.

3.2 The types of risk

The liquid you are pipetting might be:

• A toxic organic solvent
• A corrosive acid or base
• A solution containing heavy metals
• A biological sample carrying infectious agents

Historically, some laboratory-acquired infections and poisonings have been linked to mouth pipetting. This is why modern safety standards and institutional rules are unanimous: mouth pipetting is forbidden in professional labs, teaching labs and serious small labs.

3.3 Safer alternatives

Modern labs have simple tools that make mouth pipetting unnecessary:

• Rubber pipette bulbs
• Manual pipette controllers
• Adjustable volume micropipettes with disposable tips

These devices:

• Keep liquids away from your mouth
• Give you much better control over volume
• Are inexpensive compared to the cost of an incident

A good habit is:

If you ever see mouth pipetting in a lab, treat it as an urgent safety issue, not a matter of “style” or “speed”.

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4. Second-hand and returned glassware: treat as “unknown”

Second-hand lab glassware and customer returns can be valuable resources, but they also carry invisible history.

You often do not know:

• Exactly what was in them last time
• Whether they were used correctly or misused as temporary containers
• Whether residues have dried on surfaces, joints or threads

4.1 Handling second-hand or returned glassware

When you unpack or inspect second-hand or returned glass:

• Assume that it may carry unknown contamination.
• Whenever possible, wear appropriate gloves.
• Avoid touching your face, phone or personal items during inspection.
• After handling, wash your hands thoroughly before eating, drinking or leaving for a break.

This applies both in a lab that buys second-hand glassware and in a glassware factory or warehouse that handles returns.

4.2 Cleaning before use in experiments

Before using second-hand or returned glassware in experiments:

• Put it through a thorough cleaning cycle:
  • Suitable detergent wash
  • Multiple rinses with tap water and then deionised/distilled water
  • Special cleaning procedures as required by your lab
• If the previous use is unclear and the potential risk is high, your lab may decide to discard the item rather than reuse it.

A simple principle is:

Treat any glassware of unknown history as a potential chemical container until it has been properly cleaned.

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5. Building safer everyday habits

Rules only help if they translate into daily habits. The key behaviours for reducing ingestion risk are simple but powerful:

5.1 For eating and drinking

• Keep all food and drink out of the lab.
• Never store food or beverages in lab refrigerators or freezers.
• Before eating, drinking or smoking:
  • Leave the lab
  • Remove gloves and other contaminated PPE
  • Wash your hands thoroughly with soap and water

5.2 For pipetting and liquid handling

• Never pipet by mouth, even “just water” – habits transfer across tasks.
• Use pipette bulbs, manual controllers or micropipettes.
• Store pipetting devices and tips in a clean area, away from direct contamination.
• Train new lab members explicitly: “We do not mouth pipet, ever.”

5.3 For second-hand and returned glassware

• Treat unknown glassware as contaminated until cleaned.
• Wear gloves when inspecting or sorting.
• Wash your hands after handling, before any break or meal.
• Do not assume that “it’s just glass” and therefore safe.

Small actions repeated every day—no food in the lab, no mouth pipetting, washing hands—create a long-term barrier against serious incidents.

6.Checklist: before you eat, drink or leave the lab

Before you eat, drink or leave the lab, run through this quick checklist:

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7. Mini quiz: what is the real problem?

8. Safety note

Information on ChemNorth is for educational purposes and for small-lab guidance. Always follow your institution’s safety rules and local regulations. If you are unsure whether a behaviour is safe, ask your instructor, lab supervisor or safety officer before proceeding.