The rate of Americans developing a rare meat allergy from tick bites is rising, researchers say, and may have already impacted as many as 450,000 people.

New data released by the Centers for Disease Control and Prevention (CDC) on Thursday shows a steep increase in cases of alpha-gal syndrome.

The allergy triggers a possibly life-threatening reaction to several types of meat or animal products.

US scientists have traced alpha-gal to saliva from the lone star tick.