Why eating hot cross buns can make you fail a breathalyser test

A new viral video shows how eating hot cross buns can lead to drivers failing an immediate breath test.

Footage was uploaded to the Pilbara Heavy Haulage Girls' Facebook page showing founder Heather Jones chomping into the Easter bun.

She then blows into a breathalyser and the reading shoots up to 0.018.

"If you're driving a truck, be very careful," she says. "Be really careful this Easter."

In New Zealand, the legal limit for drivers aged over 20 years is 0.05. For drivers under 20, the limit is zero.

The strange occurrence has been studied by scientists, who published about the effect in the Canadian Society of Forensic Science Journal.

They showed that some foods and beverages, including white bread, soft drinks and energy drinks, can create a mouth alcohol effect immediately after consumption - creating a positive test.

But New Zealand police say anyone thinking about blaming an innocent bun for failing a breath test needs to think again.

"New Zealand Police uses both screening and evidentiary breath testing to confirm a positive breath alcohol screening test to a precise level," a police spokesperson told Newshub.

"Evidentiary equipment takes a full sample of breath, so is therefore not as susceptible to error introduced by the mouth alcohol effect that may show immediately after the consumption of certain foods.

"The study also notes that the maximum reading after ingesting the non-alcoholic soft drink dissipated entirely after 90 seconds of ingestion."