Dick Swanson's office on the 13th floor of the Parklawn Building in Rockville is beginning to look a bit like a convenience store: his desk, side and end tables are piled with popular nonprescription drug capsules for everything from headaches to the common cold, a jar of peanut butter, boxes of cookies, disposable diapers and baby food jars.

The products have all been under investigation at the Food and Drug Administration because of alleged tampering around the country. Over the past three months, the emergency command center that Swanson heads has been inundated by a torrent of tampering complaints that only recently has begun to slow.

The trigger was the Feb. 8 death in Yonkers, N.Y., of 23-year-old Diane Elsroth after she took Extra-Strength Tylenol capsules laced with cyanide. Her killer is still at large, and the incident created a new national nightmare for officials at the federal agency charged with ensuring the safety of the nation's food and drug supply.

The tremendous effort to track tampering complaints, real and imagined, has cost the already overtaxed FDA a major loss in manpower, not to mention an estimated $1.5 million in overtime by its field staff. "We treat each case as a full follow-up," says Swanson, whose small office was staffed for 54 days straight following the Elsroth death and remains on 24-hour alert.

"We still have a great deal of confidence in the food and drug supply in this country," emphasizes Swanson, a bearded bureaucrat who is reluctant even to talk publicly about tampering for fear of inciting further incidents.

He notes that, aside from the Tylenol capsule homicides -- the seven Chicago deaths in late 1982 and the Elsroth death this year -- there have been no other serious illnesses or deaths attributed to tampering.

But numerous interviews and data provided in response to inquiries by The Washington Post provided new information about the patterns and breadth of tampering this year, its tremendous impact on the agency and the role publicity plays in tampering scares.

FDA officials, increasingly concerned about the contagious nature of a major tampering episode, have struggled to balance the public's need to know about a potential health danger against the danger of sparking more tampering.

"I compare it to a skipping stone across a pond, leaving a series of ripples in its wake," says FDA deputy commissioner John A. Norris.

Although the numbers are still incomplete, tampering complaints nationwide reached 1,900 during the six weeks following the Elsroth death, and only began to return to normal in April. This is far more than the total accumulated reports that FDA had categorized as possible tamperings since it began keeping such reports in the late 1970s.

The products cited most often in complaints were Tylenol products, Gerber baby food, Girl Scout cookies and SmithKline Beckman Corp. over-the-counter drugs Contac, Dietac and Teldrin. More than 800 complaints involved a multitude of other products, from soft drinks to peanut butter.

In comparison, in the three years following the Tylenol poisonings in the Chicago area, FDA's tally of confirmed and unconfirmed tampering-related complaints totaled less than 800. Prior to the October 1982 Tylenol episode, all recorded tampering complaints totaled 37.

A highly publicized tampering also provokes a dramatic increase in product complaints of all kinds about everything from strange-tasting items to swollen cans, discoloration or insect parts in the package.

There have been three major peaks in overall complaints, all coinciding with tampering problems. After the Chicago Tylenol poisonings, the number of complaints per month rose to 2,400.

A second peak occurred in April 1984, following allegations that Girl Scout cookies had been found to contain items such as staples, pins and glass. Overall complaints to FDA rose to nearly 2,000 that month, but an extensive follow-up investigation by the agency and the Federal Bureau of Investigation concluded that most of the reports about the cookies were children's pranks, mistakes and hoaxes.

Total complaints for last February, after Elsroth's death, rose to 1,800, and to nearly 2,200 in March.

According to William Grigg, FDA director of press relations, "We've got a serious problem when one highly publicized tampering produces so many 'me, too' reports, not only other tampering but a rash of false reports and even instances when mothers actually put substances in their own children's food, probably in hopes of suing somebody, but sometimes just to get publicity."

"Somehow, while we urgently investigate these potentially serious situations, we nevertheless have to show the media and the public that most of the incidents they hear on the local news will turn out to be mistakes and false reports, normal manufacturing deviations or of no health consequence," says Grigg.

Following the discovery of a second poisoned bottle of Tylenol in the same region where Elsroth died, public concern was further fueled by a false alarm Feb. 23 when a cyanide poisoning victim died in Nashville, Tenn., with a Tylenol container in his bed. Authorities later ruled the death a suicide, but not before tampering reports of all sorts shot up again.

In all, the FDA examined 1.5 million Tylenol capsules, finding no more poisoned bottles and no manufacturing problem. Yet FDA received a total of 495 complaints about possible Tylenol tampering in February, March and April.

Meanwhile, a report of glass in a Gerber baby food jar in upstate New York, only four days after the Elsroth death, started a spurt of tampering allegations involving baby food jars: 194 complaints in February, 290 in March, and 40 in April.

In examining more than 50,000 Gerber jars to see if there was a manufacturing problem, the FDA found only 13 jars with very small glass fragments, "smaller than a grain of wheat," says J. Paul Hile, associate commissioner for regulatory affairs.

FDA concluded that for a variety of reasons, people purposely put larger pieces of glass in baby food after it reached the retail level or even their homes, that some falsely reported it and that others were mistaken about seeing glass.

Compared to their own aggressive publicity about the possible Tylenol threat -- which involved the danger of cyanide -- FDA officials say that they purposely took a low-key approach to threats of glass in baby food. Although frightening to parents, small pieces of glass in baby food have not posed a major health risk, beyond minor cuts, they say. Gerber did not recall any products and instead vigorously defended itself against the publicity.

In late March, when an extortionist calling himself "Gary" threatened SmithKline Beckman that he had put cyanide and a rat poison in several of its popular products in two cities, the alarmed company alerted the public to stop using the drugs. FDA Commissioner Dr. Frank E. Young and Norris called a national news conference to warn against the "terrorist" threat. There were 67 complaints against SmithKline Beckman products in March.

If publicity serves as an incitement, the FDA is hopeful that prosecutions under the 1983 antitampering law will serve as a deterrent.

Local laws differ, but federal law provides penalties of up to three years in prison and $10,000 for tainting a product, rising to $100,000 and 20 years if a serious injury occurs or up to life in prison if a death occurs. False tampering reports may mean a $25,000 fine and up to five years in prison. Some recent tampering-related arrests around the country have included one for extortion, one for child abuse and six for false reports.

But Young also warns that consumers need to exercise caution. He recommends that purchasers examine carefully every food or drug before using it, looking for discoloration or such signs of prior opening as sticky jars or stained labels.

While manufacturers can add packaging to discourage tampering, he stresses that "tamper-resistant is not tamper-proof."