PSA: Don’t Microwave Water Again Before Reading This

Microwaving water may seem like an easy go-to for a quick cup of tea—even though this habit is the bane of every British tea lover’s existence. It can also feel tempting to heat up water that way for a late-night bowl of noodles. However, if you’re microwaving water without anything else in the vessel, this practice could be more problematic than just shaking up tradition.  

Zapping water solo in the microwave rather than in a tea kettle or pot on the stove can be dangerous and leave you with potentially serious burns. It all comes down to the science of how water heats up in the microwave. 

Wait, why is microwaving water dangerous?

“Microwave radiation interacts with water molecules in the center of a bowl or cup of water, causing them to quickly vibrate,” says Bryan Quoc Le, PhD, a food scientist and founder of Mendocino Food Consulting. “This increases their temperature in very specific regions, causing steam to rapidly expand and explode.”

While boiling water on the stove provides a more even distribution of heat, the microwave can quickly bring pockets of water to a boiling point, even if the surrounding regions are still at room temperature. On top of this, while water heats in the microwave, the surface tension isn’t always broken by a rolling boil the way it would in a kettle or pot. So when you do go to stir the water, breaking that tension can lead to explosive results.

Beyond the risk of volatile liquids, unevenly heated water can lead to serious burns if you’re not paying attention. Orthodontist Mohamad Khorshid, DDS, has treated patients with oral burns caused by overheated liquids, including those heated up in the microwave. “Because microwaves heat unevenly, liquids can become heated above boiling without visible bubbling,” says Dr. Khorshid. 

There are a few unique risks of this, he adds:

• No warning signs: Your water may appear stable, but can erupt violently or cause instant scalding the moment you touch it. 

• Quick tissue damage: The mucosal tissues in your mouth and throat are very delicate and rich in nerves, so even short exposure to superheated liquids can cause serious damage. 

• Potential lung damage: If you gasp reflexively from pain, you may inhale hot liquid and burn your airway or lungs, which is a medical emergency. 

Oral burns from microwaved liquids usually affect the roof of your mouth, tongue, lips, and pharyngeal mucosa (the lining of your throat), says Dr. Khorshid. 

While first-degree burns can cause redness, mild swelling, and discomfort, more serious second-degree burns could cause blistering, peeling of the mucous membrane in your throat, and more severe pain. Third-degree burns are rare with microwaved water, but could occur from prolonged contact with superheated liquids and cause ever deeper tissue damage. 

If you notice any of the following symptoms after gulping hot microwaved water, it’s time to see a doctor:

• Blistering or peeling in your mouth
• Pain that lasts longer than 48 to 72 hours
• Difficulty swallowing or breathing
• Hoarseness or throat tightness (may be a sign of airway burns)
• White patches or ulcers that don’t resolve in a week (may be a sign of secondary infection or delayed healing)
• Fever or malaise (may be a sign of systemic infection)

So, what should you do instead?

Of course, the best option is to avoid microwaved water burns in the first place. “As an orthodontist, prevention is critical, especially since many patients with appliances like braces or clear aligners have more delicate oral tissues,” says Dr. Khorshid.  

If you must use the microwave, here’s what Dr. Khorshid recommends:

• Stir and let sit: Always stir microwaved liquids and wait 30 to 60 seconds before consuming.

• Use a thermometer or finger test: Use a kitchen thermometer or test with a clean finger on the side of the cup (not in the liquid) to judge heat.

• Avoid heating in closed containers: This can cause pressure build-up and splatter, increasing burn risk.

• Use microwave-safe mugs with wide openings: They allow even heating and prevent concentrated hot spots.

• Educate children and elderly: They’re at higher risk due to slower reaction times or less sensitivity to early burn signals.

• Remove aligners before drinking hot beverages: For those with clear aligners, burns can trap heat under the plastic and worsen injuries.

That said, to remove the risk of microwaved water explosions and burns altogether—let’s just agree to use the tea kettle, shall we? Your British friends will give a collective sigh of relief.