Blood sucker: An adult paralysis tick. Credit:Virginia Bear ''What people generally do not realise is that a mammalian meat allergy can be a very serious life-threatening allergy,'' Cowdery says. Her husband, former NSW director of public prosecutions, Nicholas Cowdery, has been bitten hundreds of times but hasn't been affected. Cowdery became ''case No. 23'' for Associate Professor Sheryl van Nunen, a clinical immunology specialist at Royal North Shore Hospital. Van Nunen has more than 450 patients on her books and is seeing about two new cases a week of tick-induced allergies to red meat. It is beef, pork, lamb, not chicken or fish that is the culprit. What these patients have in common is a history of tick bites, particularly in the leafy and bush-bound suburbs of Sydney's northern beaches and north shore. However, more new cases of mammalian meat allergy are being reported all over Australia within the eastern coastal range of ticks that extends up to 20-30 kilometres inland from the sea. The Gold Coast hinterland is a hotspot, but recently Melbourne had its first case diagnosed.

And while van Nunen was the first immunologist in the world to describe the link between ticks and this otherwise virtually unknown allergy in 2007, US research has since further explained how the allergy is passed on. A recent paper published by Springer Science noted that by 2012 it was clear there are also thousands of people affected by tick-induced meat allergies in the US and Europe. An Australian study by a group of emergency medicine specialists published in the journal of Emergency Medicine Australia earlier this year, reported more than 500 cases of tick reactions at the emergency department over two years at Mona Vale Hospital on Sydney's northern beaches. The induced mammalian meat allergy is unusual in that the onset of the allergic reaction, which ranges from mild gastric symptoms to life-threatening anaphylaxis, can occur up to three to six hours after eating meat and often many months after the tick bite. Other better known tick allergies show immediate anaphylaxis, large local rashes and swelling around the bite, paralysis in young children (as well as pets) and various infections, including so-called ''tick typhus'', a flu-type condition transmitted in much the same way as a mosquito transmits malaria. In the tick season, up to two per cent of the caseload coming into emergency at Mona Vale hospital, several cases a day, are tick-related, says Dr Andy Ratchford, the hospital's director of emergency medicine, and co-author of the Australian study.

''People know about bees and peanuts, but by far the most common allergic reactions we see are to ticks and they can be just as life threatening,'' he says. A critical issue, he says, is not to squeeze a tick but to kill or paralyse it with a freeze spray before removal to prevent it injecting its saliva. Rachel Nazha, of Ryde, was relieved to get a diagnosis for her son, Adam, who had debilitating, chronic stomach problems for years every time he ate meat. They started when he was eight after a school camp in the Royal National Park where several students were bitten by ticks. ''He would be hunched over and couldn't walk. We didn't know what it was so we just started eliminating things, starting with chocolate, and it we worked out that it seemed to be meat but we'd never heard of a meat allergy.''

Eventually, they were referred to Royal North Shore Hospital where the allergy was confirmed. The only treatment is avoidance and managing the diet to ensure the adequate intake of nutrients such as iron, and carrying a precautionary EpiPen. Despite their best efforts, Adam, now 13 and a keen competition skier, became violently ill after toasting marshmallows around the fire with friends after a day on the mountains. They now know marshmallows contain beef gelatine. Janelle Williams, from the northern bush suburb of Oxford Falls, struggled for four years with what she thought could be chronic fatigue and what some doctors even suggested ''was in her head''. ''It has totally changed our lives … we need to be very careful with food and I show my allergy card everywhere I buy food outside the home,'' she says. Her daughter, too, has the allergy, making play dates and outings complicated. Van Nunen says the scientific community now understands how an allergy to meat can be induced by a tick.

All mammals, except human and higher apes, have a carbohydrate called ''alpha-gal'' in their systems. When a tick feeds on the blood of a mammal such as a bandicoot, possum, cat or dog, it introduces alpha-gal into the tick's alimentary tract which the tick transfers to the next host when it attaches. The immune system of an allergic human who is bitten recognises alpha-gal as foreign so produces allergens to fight it off, inducing delayed allergic reactions to mammalian meat. Alpha-gal in a human can now be recognised through a blood test. But people allergic to tick bites and who have an immediate reaction are reacting to proteins in the tick's saliva. There is no hard scientific evidence, however, to explain why tick allergies are reaching epidemic proportions. But, the increasing numbers correspond to two trends. First, fox baiting and bush regeneration across many areas of northern Sydney has allowed bandicoot numbers to recover and they often roam close to homes. Second, warmer conditions have coincided with more ticks. Ian Dunlop, the high-profile international oil, gas and coal industry executive turned climate change campaigner, discovered he had a serious anaphylactic allergy to ticks last year after being bitten while gardening at his Gordon home in Sydney's north. ''The biggest problem is you feel your throat starting to become constricted - the moral of the story is people really need to take this seriously,'' Dunlop says.

Van Nunen, one of the founders of the Tick-induced Allergies Research and Awareness (TIARA) fund at Royal North Shore Hospital, says getting information out about how to deal with ticks and how to recognise allergic reactions is critical. Eight years on, Cowdery is still confronted with incredulous reactions from people who say ''you really can't eat meat?''. ''It has changed summer barbecues, but now about four or five of our neighbours have the same meat allergy. ''I just wrap up some fish and bring it with me, so it doesn't touch the meat on the hotplate.''