Why do we get a runny nose when we eat spicy food?

Photo: Special Arrangement

D. Janani, Chennai.

As a defence system against animals and birds destroying plants, certain chemicals are found in the plant’s tissues. Capsaicin also known as Allyl isothiocyanate is one of such chemicals found in chillies in very high quantity in the placental tissue that holds the seeds, as well as in lower concentrations in other parts of the fruit. Allyl isothiocyanate, in the form of a colourless oil is also found in plants like mustard and radishes. Like capsaicin, it serves as a defence for the plant against various animals. It also works as an antifungal agent.

These chemicals when eaten in good amount end up not only causing a “hot” sensation on our tongue, but also irritate the mucous membranes in our nose, causing them to become inflamed. This triggers those membranes to produce extra amounts of mucous as a defence mechanism to try to keep out whatever unwanted substance or particles are causing the irritation. Our eyes may also become watery when we eat very spicy foods. The capsaicin or allyl isothiocyanate can irritate the membranes in our eyes, causing the tear ducts to kick into overdrive trying to wash the irritant away. This can make our nose even more runny as some of the tears drain into your sinuses. Capsaicin and allyl isothiocyanate also irritate various tissues inside our body, such as the intestines. This causes our body to react by trying to flush the irritant out. This is why after eating spicy foods we sometimes have the dreaded “liquid fire” poop.

From Rashmi Jain, Greater Noida, Uttar Pradesh

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Unlike in animals and plants, why is it that all humans belong to one species?

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