Doctors say a 47-year-old man who passed away in the summer of last year, had a severe reaction to a steak after spending a day in the outdoors.
He became severely ill but recovered, so he thought nothing of it.
Then, two weeks later, he died after eating a hamburger.
The allergy is known as "Alpha-gal syndrome."
The allergy is caused by the bite of the Lone Star tick.
According to University of Virginia Health, people who become sensitized to the sugar can have allergic symptoms such as rash, nausea and vomiting after eating beef, pork or lamb.
Researchers have feared that deadly anaphylaxis was possible in severe cases but had not confirmed a fatality from the allergy until now.
"The important information for the public is: First, that severe abdominal pain occurring 3 to 5 hours after eating beef, pork or lamb should be investigated as a possible episode of anaphylaxis; and, second, that tick bites that itch for more than a week or larvae of ticks often called 'chiggers' can induce or increase sensitization to mammalian-derived meat," said Platts-Mills, former chief of UVA Health's Division of Asthma, Allergy and Clinical Immunology.
The man was an airline pilot.
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