Consumer groups are calling for warning labels on food packaging containing latex, saying the substance poses a potential threat to people with allergic sensitivities. They point to a recent British study revealing that one third of food packaging tested was contaminated with latex.

According to the study, the latex was transferred to food in some cases. In one unnamed chocolate biscuit, the amount of latex found was 20 times the level that instigates a reaction. A group of experts from the UK Latex Allergy Support Group Advisory Panel said that these results were significant.

"For a few people, natural rubber latex is a very potent allergen and for these individuals, there is no safe level of exposure," said LASG representative Graham Lowe.

"We would welcome an approach to the EU to consider this evidence and the issue of labeling," he said. Lowe added that latex transfer to food could account for some currently inexplicable reactions.

There is no agreement on a safe level of latex, but it has been reported that a billionth of a gram (1ng/ml) can be enough to cause a reaction. Currently manufacturers are not required to label food packaging as containing latex.

Scientists at Leatherhead Food International measured the presence of four major latex allergens in 21 types of food packaging for confectionary, fruit and vegetable produce, meat, pastry and dairy products. A third of the materials tested gave positive results for the presence of latex and in some cases, researchers say, this was transferred onto the food.