How a life-threatening allergic reaction can happen so fast

In mice, specialized cells monitor for allergens and pass intel to response-triggering immune cells

mast cells and blood vessels

OUT OF REACH  Allergens travel in the bloodstream, but the mast cells (red) that trigger anaphylaxis are located outside of blood vessels (blue). Intermediary cells (green) reach in to probe the blood, then relay messages about allergens to mast cells.

H.W. Choi et al/Science 2018

Within minutes of biting into peanut-tainted food, people with a peanut allergy may find their pulse quickening, blood pressure plummeting and throat closing up.