Despite increasing awareness, diagnosing a meat allergy can be difficult.

Symptoms often develop at night, hours after people have eaten their evening meal, and for those suffering asthma, the two can often be confused.

Van Nunen describes it as an “an anytime but not an every time allergy”.

Symptoms may sometimes not appear at all, while at other times they may be exacerbated by factors including the type of meat, how it is cooked and if it is spicy, as well as whether a person drinks alcohol with it, exercises after eating or is sleep deprived.

Those who are hypersensitive can also be triggered by mammalian products such as milk and anything that contains a derivative of mammal meat – beauty products and laundry softeners containing lanolin, for example, and even supermarket plastic bags containing stearic acid. Fumes from a barbecue, or petting a cat or dog, can also trigger an allergic reaction.

Elizabeth Rowley, a mother of three who lives in Hannam Vale on the mid north coast of New South Wales, spent years going to doctors and allergy specialists, hoping they could diagnose the mystery illness that plagued her.

But many dismissed her symptoms, which began in 2006 and ranged from memory loss and brain fog to chest pain, numbness in her arms, full body aches, and breathing difficulties that led to her regularly passing out.

“[They said] ‘you’re turning into a bit of a hypochondriac – it’s not anaphylaxis – get over it’,” she recalls.

She has since set up a Facebook group to support fellow sufferers.

“It’s just mentally horrendous more than anything, just trying to find out what it was,” she says. “I thought I was going crazy.”

Remy Williams, a 23-year-old psychology student who lives in Sydney’s Northern Beaches and was diagnosed with the allergy as a child, says the constant vigilance of watching what she ate tipped over into an eating disorder.

But the even bigger impact, she says, was witnessing the effect on her mother, who also had the allergy and twice suffered severe anaphylactic attacks on aeroplanes.

It was “incredibly scary,” says Remy. She “literally almost died in front of me.”