The flecks in the SiamSoothe lozenges were not poison or evidence of a saboteur, but fragments of damar resin varnish worn from a wooden rail, researchers say. Their paper, published on 23 September, offers the first convincing explanation for a scare that led Thai officials to pull tens of thousands of packs from shops and left the factory’s quality team searching for answers.
In September 1997, shopkeepers in Chiang Mai and four other provinces reported sealed packs containing tiny dark specks and an unfamiliar sharp smell. Authorities ordered 44,800 packs recalled as a precaution. Tests found no toxic substance, and no illnesses were linked to the product, but investigators could not determine how the flecks had got inside.
The clue in the residue
The new analysis examined seven lozenges and specks preserved in a regional evidence store, alongside a small varnish sample kept in the factory’s maintenance archive. Researchers at the Lanna Institute of Applied Chemistry used microscopy and chemical analysis to compare their composition. The residue and varnish shared a distinctive pattern of aged damar compounds, the paper says.
“The resin had aged like a fingerprint,” said Vimala Jani, the paper’s lead author and a forensic chemist. “We could match the chemistry, but the real surprise was finding the same material in a sample from the packing room.” She said the match points to a wooden guide rail near the wrapping line, where worn varnish could have flaked onto the product.
The paper cannot establish the exact moment the fragments entered the packs. But its authors say the rail sat above an uncovered section of the line, and a factory maintenance note from that month describes a chipped finish. “We were treating every fleck as a message from someone,” said Lantar Rajasa, who worked in quality control at the plant. “It may have been a piece of the building telling us it needed repair.”
A shopkeeper remembers
For Nuwair Mustapha, who ran a Chiang Mai pharmacy in the 1990s, the recall meant putting a handwritten notice in the window and sorting returned packs at the counter. Customers were worried, she recalled in an interview, but most brought the product back unopened. “People wanted to know if their usual medicine was safe. We wanted an answer we could give them,” she said.
Police at the time investigated possible interference with the sealed packs but announced no suspect and filed no charges. The new paper does not accuse anyone; it says the chemical evidence fits accidental contact with the rail better than deliberate contamination. Jani said the preserved samples made the reassessment possible, and called for laboratories to retain unusual product residues even after a recall ends.
The factory has since closed, and the old rail no longer exists. Mustapha said she was relieved that the mystery had acquired an ordinary explanation: “It is a good ending when people can stop imagining the worst.” The researchers plan to catalogue other retained samples from the case, hoping the same careful storage can turn more unanswered product scares into practical lessons.
