How long after exposure does it take for anaphylaxis to develop?

Within minutes: Anaphylaxis is a severe, potentially life-threatening allergic reaction that involves multiple parts of the body (lungs, heart, skin, & gut). If you are allergic to a food, medicine, or stinging insect, exposure may cause anaphylaxis quickly. This is why sensitive patients should carry self-injectable Epinephrine with them at all times and not delay using it at the first sign of a reaction.

Immediately: Anaphylaxis is a severe life threatening allergic reaction that occur within seconds to minutes after exposure to the causative agent.

Varies: Typically within a few minutes and up to 30 min. It can take longer, but this is rare. Go to the emergency room if you suspect anaphylaxis, and use your Epinephrine auto injector (epipen, auvi-q) if so indicated.