What Every Parent Needs to Know About Biphasic Reactions

Learn why children must be monitored carefully long after the initial symptoms of a severe allergic reaction abate.

If your child or one of their playmates suffers from severe allergies, hopefully you are already acquainted with the risk of anaphylactic shock and aware of the steps that must be taken to prevent this shock from being fatal.

But what you may not realize is that the danger of anaphylactic shock is not over once the initial symptoms have passed. A second reaction or biphasic reaction may occur even without any further contact with the allergen. This reaction could be equally severe or even more severe than the first reaction.

New Research on Biphasic Reactions

In a small study recently published in the journal Annals of Allergy, Asthma, and Immunology, nearly 15 percent of kids experienced a secondary reaction after being treated in the emergency room for an initial episode of anaphylactic shock. The majority (75 percent) of these reactions occurred within 6 hours of the initial episode. Half of the secondary reactions were considered serious, requiring further treatment.

The study helped to identify some probable risk factors for biphasic reactions in kids with severe allergies:

• Having more severe first reaction
• Needing more than one dose of epinephrine for the first reaction
• Not getting immediate epinephrine treatment for the first reaction
• Being age 6 to 9

Take-Aways for Parents

The following steps can help parents (and caregivers of all kinds) successfully manage episodes of anaphylactic shock and guard against biphasic reactions:

1. Know the signs of anaphylactic shock. In the event of a severe allergic reaction, prompt treatment is necessary not only to minimize the chances of fatal anaphylaxis but also to reduce the risk of a secondary reaction. Although the early symptoms of a reaction may be mild, such as a runny nose, a rash, or what a child might report as a “strange feeling,” these symptoms can quickly progress into serious issues including difficulty breathing due to swelling of the face and throat, unconsciousness due to a drop in blood pressure, or even cardiac arrest. It is important for parents to recognize these signs of a severe reaction in order to ensure appropriate treatment.
2. Ensure prompt medical treatment. If the child in question is known to have a severe allergy, hopefully they will already have an epi-pen for administering epinephrine. It is better to err on the side of caution and administer the epinephrine right away even if you are not sure how far the symptoms will progress. If necessary, do not be afraid to administer a second dose. Of course, the child should also be taken to the emergency room right away.
3. Observe the child for 6 hours. Since most biphasic reactions will occur within 6 hours of the initial reaction, children must be observed closely for this period of time. In the case of a severe reaction, observation should take place in the emergency room.
4. Schedule a follow up visit with an allergist. After any type of allergic reaction—and certainly after a biphasic reaction—a visit to the allergist is in order. This is wise even if you believe you already know all about your child’s allergies. Allergies can change as a child grows, and your allergist may be able to recommend changes in medication or in allergen avoidance techniques that will help protect against future problems.

If you have any questions about your child’s allergies, we invite you to schedule an appointment ASAP at any one of our convenient clinic locations.