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

Symptoms often develop at night, hours after eating dinner, and for asthma sufferers, the two can often be confused.

Van Nunen describes it as “an allergy at any time, but not always.”

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

Hypersensitive people can also be triggered by mammalian products such as milk and anything that contains a derivative of mammalian meat: beauty products and fabric softeners containing lanolin, and even plastic grocery bags containing stearic acid. Fumes from a barbecue or petting a cat or dog can also cause an allergic reaction.

Elizabeth Rowley, a mother of three living in Hannam Vale on the mid-north coast of New South Wales, spent years seeing doctors and allergy specialists, hoping they could diagnose the mysterious illness that afflicted her.

But many ignored her symptoms, which began in 2006 and ranged from memory loss and mental confusion to chest pain, numbness in her arms, aches throughout her body and breathing difficulties that led her to regularly faint.

“[They said] “You’re becoming a bit of a hypochondriac; it’s not anaphylaxis; get over it,” he reminds.

Since then, she has created a Facebook group to support other patients.

“It’s mostly mentally horrendous, just trying to figure out what it was,” he says. “I thought I was going crazy.”

Remy Williams, a 23-year-old psychology student who lives on Sydney’s Northern Beaches and was diagnosed with allergies as a child, says constant monitoring of what she ate turned her into an eating disorder.

But the even bigger impact, he says, was witnessing the effect on his mother, who also had allergies and suffered two severe anaphylactic attacks on airplanes.

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