HOW COME? Your nose knows when the heat is on

Why does your nose run when you have a spicy meal? asks a reader. How come when you eat spicy, hot food, you feel like drinking water? (And does it really help?) asks Edward Mojica, a student in Brookville.

Find yourself sniffling over the green curry in a Thai restaurant - and you don't feel a bit sad? If so, you may have food-induced rhinorrhea. Which sounds much worse than what it is: that annoying runny nose associated with eating foods such as chili peppers, wasabi and hot mustard.

Spicy add-ons get their fire from different molecules, but all have similar effects. Chili peppers make the tongue burn and the nose run. Hot mustard and wasabi seem to concentrate their effects on the nasal passages.

Hot mustard and wasabi get their bite from mustard oils called isothiocyanates. Most of the fire of hot peppers comes courtesy of a compound called capsaicin. Contact with capsaicin causes nerves to fire off the same "pain" signals as if the tongue were exposed to actual heat. In fact, the tongue is so sensitive to capsaicin that we feel the burn when 10 parts per million lurk in an innocent-looking sauce.

Peppers even have their own rating system, a hotness scale devised by pharmacist Wilbur Scoville back in 1912. At the bottom is the green bell pepper, rating 0 Scoville units (in other words, not hot at all). An ordinary jalapeño jumps to 4,000 units. The Tabasco pepper burns in at 40,000 units. And a fiery orange habanero can pack a blistering 300,000 units on the Scoville scale. One Red Savina habanero was tested at a record 577,000 units, crossing the boundary from food into OUCH. By comparison, pure capsaicin, the hot chemical itself, blasts off the scale at 16 million Scoville units.

According to studies, food-induced runny nose syndrome, aka gustatory rhinitis, begins within minutes of eating hot, spicy foods. (Not surprisingly, eaters rated "bread" lowest on a survey of foods that might trigger their watery symptoms.) Researchers think that capsaicin and the other fiery chemicals stimulate trigeminal nerve endings near the upper respiratory and digestive tracts. A nervous-system reflex dilates blood vessels in the nose; mucus production ramps up. And the nose runs. (Which is why hot peppers and hot mustard are traditional remedies for a stuffed-up nose.)

Grabbing a handy napkin may take care of your overflowing nose, but what about your burning tongue? Does gulping that glass of water in front of you really help? The answer: Maybe. Plain, room-temperature water won't do much to remove spicy oils from your tongue (oil and water really don't mix). But ice water can cool your mouth, relieving some of the burn.

According to studies, what really works is cold, whole milk. The milk protein called casein is attracted to fat. So casein will bind, for example, to the fatty tails of capsaicin molecules - clearing them from the mouth like a detergent carrying grease away from clothing.

Sugary solutions, studies show, can help quell the burn. So the ideal spicy-meal chaser may, in fact, be a frosty milkshake.