The real side effects of drinking hot water, including the one that most articles on this topic leave out entirely.
A steaming mug has become shorthand for a healthy morning. Warm fluids genuinely do soothe an irritated throat, and any fluid helps with hydration. The side effects of drinking hot water are not about the habit, they are about the temperature, and there is one finding that deserves to be at the top of the page rather than missing from it.
In 2016 an IARC working group classified drinking very hot beverages, above 65 degrees C, as probably carcinogenic to humans (Group 2A), on the basis of evidence relating to cancer of the oesophagus (1). That is the headline. Everything else follows from it.
Key Takeaways
- IARC classifies beverages above 65 degrees C as probably carcinogenic to humans (1).
- In a 50,045-person cohort, tea at 60 degrees C or hotter carried a 41% higher risk of oesophageal squamous cell cancer (2).
- Very hot water can burn the throat, and swelling may build over hours (4).
- Use cold tap water for drinking and cooking, then heat it (5).
- Warm, not scalding, keeps the comfort without the risk.
What the Research Shows
Save| Finding | What was measured | Result |
|---|---|---|
| IARC classification, 2016 | Working group review of drinking very hot beverages | Very hot beverages above 65 degrees C classified as probably carcinogenic to humans, Group 2A (1) |
| Golestan cohort, Iran | Tea temperature measured objectively in 50,045 adults, followed a median 10.1 years, 317 new oesophageal squamous cell cancers | Drinking at 60 degrees C or hotter: hazard ratio 1.41. Preferring ‘very hot’ tea: hazard ratio 2.41 (2) |
| UK Biobank | 454,796 adults, preferred beverage temperature and daily intake | 4 to 6 cups a day of hot beverages: hazard ratio 1.97 for oesophageal squamous cell carcinoma. Very hot, up to 4 cups a day: 2.52, rising with intake (3) |
| Case report | A man who drank water at an estimated 90 degrees C | Laryngopharyngeal burn with swelling that obstructed part of the airway (4) |
Two things are worth drawing out of that table.
First, the risk is about temperature, not about tea, coffee or water as such. The IARC working group found no carcinogenic classification for coffee itself; the classification attaches to drinking things very hot (1).
Second, the effect size is not trivial and it rises with how much you drink. In the UK Biobank analysis of 454,796 adults, risk of oesophageal squamous cell carcinoma increased with daily intake of hot and very hot drinks, with hazard ratios of 1.97 and 2.52 in the categories described above (3).
Burns Are the Immediate Risk
Your throat has no reliable early warning system. Water that feels tolerable on the lips can still injure tissue further down. A published case describes a man who drank water at an estimated 90 degrees C and developed a laryngopharyngeal burn, with swelling that obstructed part of his airway (4).
The pattern matters for what you do afterwards: swelling from a throat burn does not necessarily peak immediately, so someone can feel mostly fine at first and considerably worse later the same day. Difficulty swallowing, a changed voice or worsening breathing after a hot drink is a reason to seek care rather than wait.
For ordinary minor burns to skin, standard first aid is cool running water or a cool, not iced, water bath for at least several minutes (6). For the mouth and throat, rinse with cool water, sip cold fluids and get assessed if symptoms progress.
Do Not Drink Hot Water Straight From the Tap
SaveThis part is not folklore either. EPA guidance on lead in drinking water is explicit: use only cold water for drinking and cooking, and do not run hot water through a filter (5). Hot water sitting in heaters, tanks and pipework has more opportunity to dissolve metal from those surfaces, and filters are not designed for it.
The fix is trivial. Draw cold water, then heat it.
How to Keep the Habit Without the Risk
- Stay under 65 degrees C, which is the line IARC draws (1). Freshly boiled water is around 100.
- Let it stand. A few minutes in an open mug, or a splash of cold water, does it.
- Test with a small sip rather than a mouthful.
- Use cold tap water and heat it, rather than drawing hot water to drink (5).
- Be careful with children and older adults, who scald more easily and may not report it clearly.
None of this argues against warm drinks. A comfortably warm mug is soothing for a sore throat and fine every day. If you like a morning ritual, the same logic applies to the lemon tea and buckwheat tea habits we have covered, and to any drink marketed for weight loss: the temperature is the part to watch.
Frequently Asked Questions
What are the side effects of drinking hot water?
The main ones are burns to the mouth, throat and oesophagus, and, at high temperatures over years, an increased risk of oesophageal cancer. IARC classifies drinking beverages above 65 degrees C as probably carcinogenic to humans. Warm water itself is not the problem; temperature is.
What temperature is safe?
Below 65 degrees C is the line IARC draws, and the cohort evidence suggests risk starts climbing from around 60. In practice, letting a freshly boiled mug stand for several minutes, or topping it with cold water, gets you comfortably under that.
Why is tap hot water a bad idea for drinking?
EPA advises using only cold water for drinking and cooking, and not running hot water through a filter. Hot water sitting in pipes, tanks and heaters can pick up more dissolved metal, including lead, than cold water.
Does hot water help digestion or weight loss?
Warm fluids can soothe a sore throat and feel comforting, and any fluid supports hydration. There is no good evidence that hot water in particular burns fat or speeds digestion.
What should I do if I scald my mouth or throat?
Stop drinking, rinse with cool water and sip cold fluids. Seek medical care if swallowing becomes difficult, your voice changes, or breathing feels harder. Swelling after a throat burn can build over the following hours rather than appearing straight away.
The Bottom Line
Warm water is fine. Very hot water is the problem, and the evidence is stronger than most wellness articles admit: IARC classifies beverages above 65 degrees C as probably carcinogenic to humans, and large prospective cohorts in Iran and the UK both found higher rates of oesophageal squamous cell cancer among people who drank their beverages very hot. Add the immediate risk of throat burns and the reasons to avoid drinking hot tap water, and the practical advice is simple: heat cold water, let it cool below scalding, and enjoy it.
This article is for informational purposes only and is not a substitute for professional medical advice. Seek urgent medical care for difficulty swallowing, voice change or breathing difficulty after a hot drink.
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