Q: I am sometimes bothered by hives. I have never been able to associate it with any particular food, but recently I read that salicylates in foods can cause these reactions. Is this true?

A: Apparently in some individuals they can. It has long been known that acetylsalicylic acid (aspirin) can either exacerbate chronic urticaria (hives) or cause acute symptoms. Reports for the past 15 years in medical literature have indicated that a so-called "salicylate-free" diet was helpful to some who suffered from the chronic condition. But until recently, data on the salicylate content of food was severely limited.

Moreover, an individual would have to be extremely sensitive to salicylate to benefit from dietary restriction. The test dose of salicylic acid, 300 mg, is equivalent to the amount in a single aspirin. The salicyclic content of a typical western diet is estimated to range between 10 and 200 mg, spread out over an entire day.

A group of investigators from the University of Sydney (Australia) recently analyzed the salicylate content of almost 350 foods and condiments. They found that previous analyses usually underestimated the amounts present. They discovered that fruits generally contained quite a lot. Dried fruits, especially raisins and prunes, had the highest concentration, and berries also contained significant amounts. The amount in apples varied considerably by species. Salicylate content of vegetables showed great variation as well, from negligible quantities in bamboo shoots, dried beans, green cabbage, celery, lentils, lettuce and dried peas to large amounts in gherkin pickles. And while fresh tomatoes had little, many canned tomato products had appreciable amounts, probably attributable to herbs and spices, which tend to be high in salicylates.

Tea contained more than other beverages. Among nuts, almonds, water chestnuts and peanuts in the skin had more than other varieties. Finally, licorice, peppermint and some honeys contribute salicylates. Cereals, meat, fish, poultry and dairy products have little or none.

A diet that attempts to eliminate salicylates may help some individuals sensitive to these substances, but will narrow one's food choices considerably. It should be tried only after a physician has determined by appropriate testing that salicylates do indeed contribute to the problem. It should never be instituted as a self-help measure.

Q: What are arginine and ornithine? I saw them for sale in the health-food store. The saleswoman told me they are the latest thing for weight control.

A: Arginine and ornithine are two amino acids from which the body builds proteins. Manufacturers of pills containing these amino acids have claimed that they stimulate growth-hormone, but what this has to do with weight loss is unclear. Moreover, it is possible that if they do actually have this capacity, they may also stimulate other hormones, thereby altering the body's internal functioning in potentially dangerous ways.

Q: A short article I read mentioned food-borne infections traced to something called Campylobacter. I wondered if you could tell me more.

A: Over the past five years, Campylobacter jejuni has emerged as a major cause of food-borne diarrheal disease in the United States and throughout the world. The infection causes acute diarrhea, abdominal pain, fever and other symptoms that last, on average, between three and seven days.

Investigators from the Centers for Disease Control (CDC) recently analyzed data from the 23 outbreaks reported between 1980 and 1982 in this country. They point out that these episodes, which affected 748 individuals, probably represent only a small proportion of those that occurred. Not all outbreaks are reported to local health departments, and not all public-health departments report these episodes to the CDC.

Raw milk was implicated or suspected in 14 of the outbreaks. Food handling errors were identified in four others. In five more, animal foods -- including poultry, eggs and beef -- were suspected. For the consumer, the real question is how to prevent Campylobacter infections. It has been suggested that the organism may occur quite commonly in healthy-appearing cows. Since udders can be washed but not sterilized, the only way to render milk safe from Campylobacter and other pathogens is by pasteurization.

Of greater practical importance to the more than 99 percent of the population that does not drink raw milk are the basic rules of food safety. Avoid cross-contamination of foods and work surfaces (for example, scrubbing a cutting board on which meat was prepared before using it to slice tomatoes). Cooking foods thoroughly and holding them at or below 40 degrees or at or above 140 degrees Fahrenheit should protect against infection from Campylobacter.