Will consuming onions help to reduce your body temperature, or prevent heatstroke? Some common variations of this claim include applying onion juice to your skin, or even just carrying an onion in your pocket, hat, or even a bag (yes, that is commonly suggested). It seems to most commonly be touted as a prevention - or even a treatment - for heatstroke.

Suggested explanations for this "cooling" effect range from "the onion absorbs heat", to the antioxidants or antihistamines in the onion cause the effect. I can't find anything about why people think a detached onion in a bag or pocket will help with the heat, though.

Claim references:
This may be a regional belief specific to India, as I've only ever heard this from coworkers who grew up in India, and it is most prominently touted in India-related websites.

For example, the Indian company INLIFE Group suggests in a 2014 article:

Onion is a great friend in the summer. It has good heat absorbing property. Keeping one white onion in your pocket or purse will help you avoid sunstroke. Applying thick onion paste on the affected person’s forehead is also an effective sunstroke treatment.

Another example is the Times of India lists onion juice as one of 7 effective home remedies to prevent heat stroke; or the New Delhi Television website, which also lists Onion Juice as one of 10 natural home remedies to treat heat stroke:

This is one of the best remedies for treating a heat stroke. Lot of Ayurvedic practitioners suggest that this should be the first thing that you must reach out for. Applying onion juice behind the ears and on your chest can help bring down your body temperature. For therapeutic purposes onion juice is more desirable, but you can roast some raw onions with cumin and honey and have it. Raw onions in chutneys or salads can also cool your system.

Edit: My main question is about whether consuming onions helps with cooling the body, but I've included the "carrying an onion" for context, as consumption and carrying are often suggested together.

Edit 2: I should also mention that a quick pubmed and Google scholar search for onions and heatstroke don't return any relevant results.

  • I think there are bit too many different claims here. Some are obviously ridiculous.. Those about paste or juice applied... might be worth investigating... although without a control group (e.g. applying just water or cream sans onion), even if there's an effect, it's meaningless. After all, water will reduce your body temperature, that's why you sweat. – Fizz Jul 5 '18 at 21:51
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    Obviously, onion juice (or, better, garlic juice) keeps people from closing in around you in a crowd. – Daniel R Hicks Jul 5 '18 at 22:17
  • You carry your onion, I will drink sufficient quantities of water. We shall then see who keels over first on a hot summer day. (Hint: if you don't drink anything, it will be you. Despite the mashed and parboiled onion in your pocket.) – JRE Jul 6 '18 at 11:21
  • One of the ‘cures’ for bubonic plague was cooked onions! – IconDaemon Jul 7 '18 at 11:22
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    This is one of those "cannot be answered" questions, because while the claims are absolutely ludicrous, where is also no-one that ever made a study of this reaching the result "Nope, that is just bonkers"... because why would they, since this is ludicrous. – MichaelK Jul 9 '18 at 6:29

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