Nothing can clear your nostrils out better than an Indian curry or a bowl of three-alarm chili. But why?
We wondered, too. And so we found the answer: there is actually a chemical in the plants or spices of these foods that functions as a protective mechanism against animals, and when you eat it, it affects you too. Mental Floss has more on how this works:
Capsaicin is the chemical found concentrated in the placental tissue of chile peppers and allyl isothiocyanate is an oil contained in plants like mustard and radishes (including horseradish). Plants use both of these chemicals as biological weapons against predatory animals. They irritate pretty much any soft tissue they come in contact with, which is what causes the wonderful burning sensation on your tongue. But they also cause the painful sting of post-chile-handling eye contact and a seriously runny nose. When your mucous membranes get hit by these chemicals, they become inflamed and go into defense mode. This means producing mucous to trap allergens and other undesirables, and keeping them out of your respiratory system by removing them via the nasal passage.
Mental Floss goes on to note that even though nasal congestion can be temporarily relieved by spicy foods, eating them with a cold could actually make the problem worse. Eating spicy foods causes a muscle in your nose to open and allow more air in. When the spice affect is done, it will close but you'll be left with all the extra mucus plus congestion.
Life's Litter Mysteries confirms that milk is the best medicine when you are in over your head with heat:
Capsaicin has an oily quality that keeps it from dissolving in water, so even guzzling straight from the tap will do you no good, and beer contains too little alcohol to have more effect than water.
Milk, on the other hand, quenches capsaicin’s fire quite effectively, according to research published in the journal Physiology & Behavior. It contains a protein called casein, which is a lipophilic ("fat-loving") molecule that hugs the capsaicin molecules and washes them away, much like detergents wash away grease.
This same research also found that regular table sugar dissolved in cold water could be successful against capsaicin, too.