Genetically modified enzymes that are used in a wide range of household products are "potent allergens", experts have said.
New products should be assessed for their "allergenicity", researchers said after they found that exposure to such enzymes can sensitise those who encounter them in the workplace.
Genetically modified enzymes used to boost the power of cleaning products and medicines or create flavourings or aromas are being increasingly used in the food, beverage, detergent, perfume, pharmaceutical, textile and chemical industries, the authors said.
But genetically engineering the enzyme protein may change its allergenic properties, they added.
The research team examined blood samples from 813 people who work in food, chemical, detergent and pharmaceutical industries - and measured specific antibodies to artificially created enzymes
The subjects had been employed in their respective industries for periods ranging from three months to 10 years - and had been exposed to, on average, between two and four genetically modified enzymes in the workplace.
Each blood sample was tested for antibodies to various enzymes using the researchers' own diagnostic tests - the commercially available options only test for naturally occurring enzymes.
Almost one in four of the employees (23%) had specific antibodies to the genetically modified enzymes to which they were routinely exposed during working hours, according to the study, which has been published in the journal Occupational and Environmental Medicine.
The researchers said that the study was hampered by commercial secrecy, which prevented them from gaining access to the formulations used.
But they conclude: "Our findings indicate that new sources of enzymes, as well as genetically engineered enzymes, are posing potential health risks."
They added: "Genetically engineered enzymes are potent allergens eliciting immediate-type sensitisation.
"The assessment of allergenicity should be mandatory for all new products...Enzymes should be tested like any other potentially hazardous chemical."