When the McPike family reached home after eating at a restaurant in Salem, Ore., 10-year-old Medaya complained that her chest felt as if it were on fire. Medaya's parents decided to take her to a physician.

During the 10-minute ride to the hospital, Medaya turned blue, began to vomit and lost consciousness. She was brain-dead by the time she reached the emergency room. Five days later, Medaya died in the arms of her parents.

Medaya, an asthmatic, was killed by an allergic reaction to sulfite, a preservative in the guacamole and salad she had eaten that night.

The death of Medaya McPike in late February, and the deaths of a dozen other asthmatics around the nation since 1982, led to a storm of protests last week from consumer groups who want sulfiting agents banned and outrage from some members of Congress who have accused the Food and Drug Administration of failing to protect the public's health.

Restaurants commonly use sulfiting agents to make salad ingredients look fresh. Sulfiting agents also are used to prevent discoloration of shellfish, preserve packaged foods, beer and wine, and act as an antioxidant in various medications. Six agents -- sulfur dioxide, sodium sulfite, sodium and potassium bisulfite, and sodium and potassium metabisulfite -- are currently included on the FDA's "generally recognized as safe" (GRAS) list.

Because of the types of foods treated with sulfites, the highest exposure to the chemical is often among consumers who opt for salad bars and prefer wine and beer to hard liquor.

The FDA believes that 5 to 10 percent of the nation's 9 million asthmatics may be particularly sensitive to sulfiting agents. The presence of sulfites in medications used by some asthmatics may increase their total exposure, making them more sensitive to a sudden dose.

Sulfiting agents harm asthmatics because they release sulfur dioxide, a known asthma inducer, says Dr. Ronald Simon, a researcher at the Scripps Clinic and Research Foundation in La Jolla, Calif. When sulfiting agents are eaten, they release sulfur dioxide gas in the mouth, which the asthmatic then inhales.

If the sulfiting agent releases a large amount of sulfur dioxide gas, the asthmatic can literally suffocate because the asthma prevents enough oxygen from getting through the lungs and into the blood, Simon says. Without enough oxygen, the person begins producing toxic chemicals in the body, turns blue, and, as the blood pressure falls, become unconscious and goes into shock, which can be brain-damaging or even lethal.

Asthmatics, however, are not the only ones to suffer reactions to sulfiting agents. Adverse reactions seem to result from a deficiency of an enzyme that ordinarily converts sulfite into a harmless substance. Reactions can include faintness, headaches, rashes, gastrointestinal problems, difficulty breathing, loss of consciousness and death.

"We didn't know what was happening. It was all over in just minutes," James McPike says quietly as he describes his daughter's death. The McPike family had previously dined at the restaurant; in fact, Medaya, the eldest of six daughters, had ordered the very same dish, a guacamole tostada, on other occasions with no adverse reactions.

This time, however, a chemical analysis performed on the batch of guacamole by the Oregon health department showed that Medaya's meal was doused with excessive amounts of a sulfiting agent, sodium bisulfite.

According to the Center for Science in the Public Interest, if Medaya consumed even half a cup of her guacamole, she ate roughly 1,000 milligrams of sodium bisulfite. For a 132-pound adult, the World Health Organization considers the "daily acceptable intake" to be 42 milligrams.

Although a dozen people are believed to have died from sulfite exposure since 1982, some consumer advocates believe the number of victims may be much higher. "It's very hard to trace these disorders," says Ellen Haas, director of the Washington-based Public Voice for Food and Health Policy. "Twelve deaths is probably just a fraction of the actual number." There have also been more than 500 cases of adverse reactions to sulfites, mostly among asthmatics.

In October 1982 the Washington-based Center for Science in the Public Interest petitioned the Food and Drug Administration to ban or limit the use of sulfites, a request the agency turned down.

"The FDA has done nothing to protect the public against sulfites," says Michael Jacobson, CSPI director. "The FDA's disregard for public health is scandalous. This is an administration that puts antiregulatory philosophy above public health."

Last week, during testimony before the House Energy and Commerce Subcommittee on Oversight and Investigations, McPike, other consumers, members of Congress and scientists urged a limited ban of sulfites. They also accused the FDA of not acting promptly to protect the public against sulfiting agents.

"It depends on the definition of 'promptly,' " responds FDA spokesman Jim Greene. "The rule-making process is slow and cumbersome. We're moving as quickly as we can."

Greene points out that the agency advised the National Restaurant Association and state authorities about sulfites in February 1983 and again in September 1984.

The National Restaurant Association, however, represents fewer than 18 percent of the nation's 560,000 restaurants. "That doesn't cover all the bases," acknowledges Greene. "There's no easy answer."

In December 1982, the restaurant association asked the FDA to investigate sulfites, several months before the FDA first issued warnings, according to testimony before the FDA's independent board of scientists given by William Fisher, executive vice president of the restaurant association.

After the FDA came under attack last week, the Office of Management and Budget approved a proposal to strengthen requirements that processed foods be labeled if they contain sulfites.

But according to FDA Consumer Safety Officer Dr. Mary Custer, the real problems with sulfites arise from their use in restaurant salad bars. The agency, she says, receives almost three times as many complaints about salad bar ingredients as it does about packaged foods.

Salad bar ingredients, say members of Congress and consumer groups, are not affected by the new proposal. "The FDA still hasn't acted where the danger is the greatest, in restaurants. I have said that the government watchdog is asleep; this is an indication that the government watchdog is maybe raising its paw," says Rep. Ron Wyden (D-Ore.), who along with Sen. Albert Gore Jr. (D-Tenn.) proposed a ban on the use of sulfites in fresh fruits and vegetables as well as cut or frozen potatoes.

Simply labeling salad bars may not be enough to protect the public. Many consumers may not know if they are sensitive to sulfites. It's also possible to develop a sensitivity, and even those who know they are sulfite-sensitive can have difficulties avoiding the chemical.

Last year, according to Custer, a woman in California with a history of adverse reactions asked a restaurant manager whether sulfiting agents were present in the food. Assured they were not, she ate cottage fries and lapsed into a coma, which resulted in permanent brain damage. Later investigation revealed that the restaurant did not realize the distributor had omitted the sulfite label from the frozen potatoes.

"You have to know and trust your supplier," says Jeffrey Prince, senior director of the National Restaurant Association. "If I suddenly need lettuce -- my supply lines are completely irregular -- I'll get it wherever I can. How do I know what's on it?"

According to Dr. Corbin Miles, GRAS review branch chief with the FDA, no one knows to what extent these chemicals are present in the nation's food. "There's no good, reliable data on the amount of sulfiting agents used," says Miles. "You have to assume the worst -- that there's a whole lot used."

Nor does the FDA know at which level -- distributor, processor, restaurateur -- sulfiting agents are applied. "We have no idea," Custer says. "It can be applied by anyone. Suffice to say, it is applied."

Custer also points out that when sulfiting agents are used as a fungicide on fresh produce, such as grapes, they fall under the jurisdiction of the Environmental Protection Agency. Since the EPA does not require labeling when fungicides or pesticides are sprayed on fruits and vegetables, a consumer cannot detect sulfiting agents, which are tasteless and odorless. And, according to FDA sources, these chemicals cannot be washed off.

Although the main function of sulfiting agents is cosmetic -- to keep foods looking fresher than they actually are -- consumer advocates argue that ascorbic and citric acid are safe alternatives to sulfites for such uses as preventing discoloration of produce.

"I don't know if any necessary uses of sulfites exist," says Jacobson, who notes that sulfiting agents are not always used among different brands of the same food items. For example, both Townhouse and Scotch-Buy figs contain sulfites, although Sunmaid figs do not. And while Uncle Ben's British-Style Rice for Beef has sulfites, a comparable product, Rice-A-Roni Beef-Flavored Rice, has none.

Under current FDA regulations, sulfiting agents may be used as a preservative in any food, except meat or food that is a source of vitamin B1, which sulfites can destroy. But this regulation is often ignored. An avocado, like those used in the guacamole that Medaya ate, contains more vitamin B1 than steak.

"The question is," says Rep. Wyden, "if the restaurant in Oregon had obeyed the rules about the safe use of sulfites, would Medaya be alive today? The answer basically is yes."

Medaya's father believes sulfites shouldn't be used on any food, and he blames the FDA for his daughter's death. "Nothing can bring Medaya back," says McPike. "You have to lay her death directly at the feet of the FDA and say you guys didn't do your job."