On the porch of the Chilmark General Store and at sunset-watching parties on Menemsha Beach, conversations circle ineluctably to the lone star tick, which after a single bite can leave people with a life-threatening allergy to most meat and dairy.

Known as alpha-gal syndrome, the condition is changing the way many people shop, cook and eat in a place long known as a food-lover’s retreat for its thriving independent farms and restaurants.

These new habits may prove to be lasting, as some islanders who initially avoided beef and cheese temporarily, out of necessity, later give them up for good out of preference.

“It’s sort of supersized vegetarianism,” said Rebecca Miller, a farm owner who has the syndrome herself.

Last year, out of 1,254 tests for the allergy, 523 came back positive, according to laboratory data from Martha’s Vineyard Hospital. This was a stunningly fast rise from 2020, when only two out of nine tests were positive.