Biphasic response is where there are two separate and distinct responses that are separated in time. There would be an immediate reaction to the trigger which is then followed by a recurrence of symptoms after an interval of time with no symptoms or signs. This Anaphylactic reaction can happen happen between 2 and 72 hours so can happen after discharge from hospital. These second reactions can occur in as many of 20 percent of cases. The biphasic reaction can be less severe than, equally severe as, or more severe than the initial reaction, ranging from mild symptoms to a fatality.
Biphasic reactions happen in up to one-third of patients who have had a near-fatal reactions. These patients seem to have fully recovered when severe bronchospasm suddenly recurs. Predicting if a second reaction will occur is not easy but the more severe the reaction or when two auto injectors are needed the higher the chance of a recurrence. Being aware of a possible biphasic response is important if you are caring for someone so you can monitor the patient just in case. If you are just administering first aid then it may be worth telling them or their parent to watch for additional symptoms. Knowing this is important but every Anaphalatic reaction patient is sent to hospital and they will advise on the actual care they think is needed after discharge from hospital.
Always make sure you have a spare auto injector once discharged from hospital just incase and that you monitor the patient closely for up to 72 hours after the first attack. See our online Anaphylaxis Training course site.