MOUTH ABLAZE from the Sichuan chicken, a woman grabbed her water and grumbled to her companion, "How can you stand it?"

"You're right," he replied. "They never put enough peppers in this dish."

Some like it hot; some may not. The fact is, when you eat food that has been heavily spiced, the oral receptors on your tongue, palate, pharynx and esophagus feel pain. The flavor may be sweet or pungent, but the "hot" is not a taste you're responding to. Your receptors are getting burned.

Differences among heat-eaters arise from a combination of factors: environmental (by age 6, Mexican children buy candies spiked not with sugar, but with chili pepper); genetic ("if Mom and Dad had a bad stomach, you might too," said Silver Spring gastroenterologist Dr. Arnold Levy); experiential ("people will accept it more who've had it more," said Dr. Robert Henkin, director for Georgetown's Center for Molecular Nutrition and Sensory Disorders) and perhaps psychological.

As far as physical differences, there is "precious little data" to explain how people respond to hot foods physiologically, said Levy. Since "pain is subjective," studies would be very difficult to conduct, he said. Much is conjecture; there are lots of theories.

In fact, one even suggests that those who regularly eat large doses of spicy food can build tolerances by "actually killing pain fibers," said Dr. Sol Snyder, director of the Department of Neuroscience at Johns Hopkins University.

Or there's the Henkin tolerance theory. It's like getting used to a hot shower, he said. You can "gradually teach your receptors to accept higher levels of hotness."

At Texas A&M University, the department of horticulture makes it its business to learn about heat levels of peppers, breeding new varieties of varying hotnesses. Ed Burns, a food scientist in charge of the fruit and vegetable processing laboratory, said that during the department's taste tests, most tasters "block out" after eating six or eight jalapen os. They lose their sensitivity, said Burns, and then have little difficulty eating more.

The reasons why people enjoy this painful sensation are numerous. Titillation and stimulation are two, and there is a "little bit of evidence that this kind of stuff goes along with personalities that are 'sensation seeking,' " said Dr. Paul Rizon, professor of psychology at the University of Pennsylvania.

How people learn to like hot foods--specifically chili peppers--is being studied by Rizon, who has been doing research on human food choices since 1975. According to Rizon, almost everybody hates chili peppers at first bite. (Rizon's research even took him to a city in Mexico where he studied how children learn to like them.)

"When people get to like chili pepper, they like it for the same reasons they hated it," said Rozin. "People are getting to like pain." Eating chili peppers is like a roller coaster ride, said Rozin of his "benign masochism" theory. "People like to endure pain and then discover it's safe."

Another theory on why people consume "innately adversive" chili peppers is the "opponent process." When you're in pain, you generate anti-pain, said Rozin. Eating chili peppers induces pain, which stimulates endorphins (a peptide secreted in the brain that has a pain-relieving effect). Some claim, said Rizon, that you can actually "overshoot" endorphins, producing "pleasure or a high."

Besides pain, other bodily responses are at work. Or, more like it, bodily defenses. Wayne Silver, a biologist at the Monell Chemical Senses Center in Philadelphia, who is studying the electrophysiology of nerves in the nose, said that facial nerves send out protective mechanisms against irritants. Your nose may run after smelling horseradish or ginger, said Silver, to block out the fumes. Your eyes tear after cutting an onion to wash away the vapors. And eating chili peppers causes salivation, perhaps the body's way of diluting the peppers' active ingredient, capsiacin, said Rizon.

Chili peppers also can increase gastric secretion. Acid secretion along with salivation are appetite stimulators, said Rizon. So there may be something to those claims of "I want more," after the hefty portion of Thai Shrimp with Chef's Special Sauce.

It's difficult to point a finger at fiery food as the sole cause of a stomach disorder, i.e. ulcer, or a gall bladder attack. But too-hot hots can aggravate an exisiting condition. "It's like having tight shoes and a tight girdle," said Miriam Ratner, associate director of the American Digestive Disease Society.

Heartburn, though, certainly is common after eating spicy food. Heartburn results from gastric regurgitation--when food that has reached your stomach reroutes itself back to your esophagus. In addition, said Henkin, you also may be feeling the irritation of your burning receptors on the esophagus.

How to douse the hots is a much-debated topic. Folk wisdom cites beer, milk or bread, and alcohol theoretically should do it for foods spiked with chili peppers, said Rizon. Capsiacin is soluble in alcohol, not water, but Rozin said he doesn't find that it works for him.

Burns of Texas A&M said they use cream in his territory. Georgetown's Henkin said the temperature of the quencher is not as important as its ability to wash away the substance from your receptors.

There's certainly no evidence to suggest that eating hot stuff is detrimental to your health; spices have been around for thousands of years and we're still here to eat them. There may, in fact, be benefits to overloading on spicy dishes. Chili peppers, for instance, are rich sources of Vitamin C and Vitamin A.

The power of the pepper even may play a part in our future. Snyder of Johns Hopkins University said that since capsiacin can destroy pain fibers, people with intractable pain conceivably could benefit from a drug composed from it. Imagine, a chile rellenos pill.