What Do You Know about Biphasic Reaction?

woman in the grocery

Food allergy has never been a cold topic; yearly we hear the good and bad news that surrounds it and importantly, the precious lives lost due to anaphylaxis and sadly we still know little about the condition. But we’re fortunate that the information made available by researchers is enough to help people stay food allergy safe. There is a lot of this reliable information that helps better the lives of many and one of these is Biphasic Reaction.

Biphasic Reaction

Anaphylaxis is the life-threatening form of an allergic reaction that is onset and if not treated immediately may cause death.

Biphasic reaction or biphasic anaphylaxis is the secondary reaction after the initial anaphylaxis and this may occur within 1-72 hours after the first anaphylactic symptoms have subsided. There’s no way to predict this secondary reaction and it occurs without being exposed to an allergen. The median time for a biphasic reaction to occur is 12 hours after the initial reaction.

How common is Biphasic Reaction?

woman with biphasic

The biphasic reaction is not common, in fact, based on studies it is estimated to occur in 1 out of 20 patients only. Another study published in The Journal of Allergy and Clinical Immunology: In Practice, states that among the 4,114 patients with anaphylaxis only 192 of them experienced biphasic reactions.

Can we predict if a biphasic reaction will occur?

ballpen and stethoscope

Like the initial anaphylaxis, it’s hard to tell unless signs and symptoms occur. There is a study that highlights the factors of people who are at risk for secondary anaphylaxis.

  • Delay in receiving emergency room treatment
  • Delay in administering adrenaline, more than 90 minutes before the initial reaction
  • If the patient has hypotension and/or laryngeal edema
  • The severity of the primary anaphylactic reaction
  • History of a previous biphasic reaction or asthma

The Longest Wait

woman pointing her watch

It’s hard or even impossible to tell when the biphasic reaction will occur, the best thing that we can do is to wait and be open for the possibility that the second anaphylaxis has 72-hour window to attack again. This will help us be prepared and be more cautious to avoid panic and surprises. In this case, monitoring is essential so don’t rush out of the hospital after the treatment. Watch out for symptoms that may resurface gradually or abruptly and call emergency assistance right away.

So why the longest wait?

Imagine you or your loved ones, just survived an anaphylactic reaction and knowing that a second reaction may occur but doesn’t have the slightest idea when, you need to wait it out to remain inside the safety zone and we know these situations are excruciating, not only for the patient but also to their loved ones.

Safety and Precautions

With this knowledge about the biphasic reaction, carrying two EpiPens or Auvi-Qs are not only logical but also reasonable. Asking or calling an emergency hotline, immediately after administering adrenaline is a must since we’re anticipating for a biphasic reaction, and due to this don’t hesitate to use your second EAI in case the symptoms reoccur while waiting for the ambulance.




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