Q: Can my child test positive for an antibiotic allergy even if they have taken it safely before?

Medically reviewed by Sang Hyun Ahn, MD

This post is a dramatization of a question and answer session experienced by our actual medical reviewers. Please note that this content is for informational purposes only and does not constitute medical advice. Always consult with a qualified healthcare professional for any health concerns or before making any decisions related to your health or treatment.

Question:

My child has had a fever since Saturday evening. The temperature has consistently reached up to 40°C (104°F), and fever reducers aren't working well. We went to the hospital today and got a flu test, which came back negative. While receiving IV fluids, they performed an antibiotic skin allergy test, and both tests came back positive. The medical staff mentioned that one of the tested antibiotics was actually one my child had taken previously.

Is this possible? Is it okay? I am so worried that there might be a serious problem.

Answer:

You must be very worried since the high fever reaching 40°C (104°F) has continued since Saturday, and fever reducers are not working effectively. It is completely understandable that you feel even more anxious because the antibiotic tests came back positive twice.

A positive result on an Antibiotic Skin Test (AST) indicates a potential allergy to that specific antibiotic. It is indeed possible to test positive even for an antibiotic that was used safely in the past due to the following reasons:

• Antibodies might have formed: Your child's immune system may have developed antibodies after the previous exposure, even if there were no allergic symptoms at that time.

• Cross-reactivity: A reaction can occur between different antibiotics that belong to a similar class.

• False positive: The test may sometimes show a positive result even when there isn't a true allergy.

What is most important right now:

1. The medical team will select a safe, alternative antibiotic for your child.

2. Identifying the underlying cause of the high fever and proceeding with appropriate treatment.

3. Preventing dehydration through the IV fluid therapy your child is currently receiving.

Additional things to monitor:

→ What are the results of the blood tests?

→ Are there any other symptoms (such as a cough, runny nose, rash, etc.)?

→ What is your child's overall energy level and condition?

Finding the cause of the high fever and treating the infection is a higher priority right now than the positive antibiotic allergy test. Please discuss this thoroughly with your medical team; your child can still be treated safely and effectively with an alternative prescribed antibiotic.

For extra peace of mind and clear guidance when tracking your child's symptoms, the FeverCoach app is always there to help.

https://fevercoach.us