The racing heart and the difficulty breathing. The tightening of the throat. The itching, swelling, and vomiting. How important it is to have epinephrine with the person at all times.
But have you heard of biphasic anaphylaxis? It’s when a person appears to recover from anaphylaxis and everyone is finally starting to relax, but then they have a second reaction … without being exposed to the allergen again.
Experts say biphasic reactions happen more often than we’d like to believe — possibly involving 15 per cent of children with severe allergic reactions. Sometimes the second reaction is more mild than the first, but other times it’s life-threatening.
After an anaphylactic reaction, a patient is usually under observation at the hospital for 4-6 hours. In a study conducted by the Children’s Hospital of Eastern Ontario, 75 percent of the biphasic reactions occured within six hours of the original reaction.
But biphasic anaphylaxis can also strike long after the initial reaction. Patients have reported a second reaction 10 hours, 26 hours, 40 hours, and even 72 hours after their initial reaction. What if the patient used up all of their auto-injectors during the first reaction, and the second reaction hits before they’ve trekked to the pharmacy for refills?
Some people are more likely to experience biphasic anaphylaxis than others:
- Children aged 6-9
- Those who were delayed in getting initial treatment
- Those who needed more than a single dose of epinephrine during the first reaction
- Those who have a more severe, life-threatening first reaction
- Those who take longer to stabilize during the first reaction
The best way to prepare for the possibility of biphasic anaphylaxis is by carefully monitoring your child after an anaphylactic reaction, and making sure you have more epinephrine ready in case of a second reaction.