Antibiotic Allergy Testing

As many as 10 percent of children are allergic to antibiotics. If your child has had an allergic reaction to an antibiotic, a doctor may advise an allergy test for antibiotics.

Skin testing is available for penicillin. Skin testing for other antibiotics, such as cephalosporins, can be done, but the validity is uncertain. Routine skin testing for sulfa drugs (found in Bactrim or Septra), erythromycin or clindamycin, isn’t currently available.

What is antibiotic testing?

Antibiotic testing helps us to determine if your child is allergic to some antibiotics.

Why does my child need antibiotic testing?

Your child had a serious reaction to an antibiotic. Your allergist would like to do this test to make sure your child is allergic to that antibiotic.

Where is the medication/vaccine testing done?

Antibiotic testing is done in the Allergy and Asthma Program on Fegan 6 at Boston Children’s Hospital’s main campus (300 Longwood Avenue, Boston).

How should I prepare for this test?

Arrival time: Please arrive 30 to 45 minutes before your child’s test. This gives you enough time to park and register at the front desk on Fegan 6. If you’re late, your appointment may be canceled.

Diet: Your child may eat and drink as usual before the test.

Medicine: You may need to stop some of your child’s medications before the challenge. Follow the instructions below. Talk with your child’s allergist if you have questions.

• Asthma medicines: Continue to give daily controller asthma medications (examples: Singulair, Flovent, Pulmicort) as usual before the test.

DO NOT STOP giving your child medications except for those below:

• Two weeks before the test: Stop giving antihistamines, as these can affect test results. Antihistamines to stop giving your child two weeks before the test include:
  • Allegra (fexofenadine)
  • Atarax (hydroxyzine)
  • Claritin (loratadine)
  • Cyproheptadine
  • Xyzal (levocetirizine)
  • Zyrtec (cetirizine)
• One week before the test: Do not give nonprescription cold or allergy medicine, as many contain antihistamines. These include:
  • Actifed
  • Benadryl (note: you can give this up to 3 days before the challenge)
  • Dimetapp
  • Pediacare
  • Tavist
  • Triaminic

If you do not know whether your child’s medicine has antihistamines in it, ask your pharmacist or call 617-355-6117 and speak with our allergy nurse.

If you are not able to stop a medication or if your child has symptoms while off a medication, call 617-355-6117 and speak with our allergy nurse.

What to bring with you: The visit can take up to three hours. Please bring small toys, games, a tablet/phone, or books for your child to use while you are waiting.

Talking to your child: Explain in simple terms why the test is needed and what will happen. Some things you may want to say:

• "I will be with you during the test."
• "You will need to keep your arm or back very still."
• "You can bring a favorite toy into the room."

Ask a member of your health care team for the Family Education Sheet, Preparing Your Child for a Hospital Stay or Procedure, for more age-based tips.

Who will do the test?

An allergy nurse does the medication/vaccine testing. An allergist is nearby during the challenge. Please note: This is not a doctor’s visit. You will not see your child’s regular allergist.

What if my child is not feeling well the day of the test?

If your child isn’t feeling well, please let us know as soon as possible. Your child cannot be ill on the day before and the day of the medication or vaccine test. We will need to reschedule the test if you child has:

• a fever
• allergy or asthma symptoms
• diarrhea
• rash
• viral illness
• vomiting (throwing up)

Please call 617-355-6117 to reschedule the medication or vaccine testing.

What happens during the test?

Your child is tested for an allergy to a medication or vaccine. There are several stages of testing, with 15 to 20 minutes between each stage. The following tests are done during these stages:

• A skin prick test: An allergy nurse places drops of liquid onto your child’s arm or back, and presses the liquid into the skin with an applicator.
• A needle test (intradermal): An allergy nurse uses tiny needles to inject a small amount of the medication or vaccine under the top layer of skin on the upper arm.

During each stage, the allergy nurse carefully watches for an allergic reaction, which is most often a small red bump that may feel itchy at the sight of injection.

What if my child has a reaction?

If your child has a positive reaction, your child is considered allergic to that medication or vaccine. These reactions usually go away in 30 to 60 minutes.

Your child may have swelling and itching at the injection site four to eight hours after the test. You may use an over-the-counter hydrocortisone cream to help with this.

Your child may have a skin reaction at the injection site several hours after the test is done; this is called a delayed local skin reaction. This reaction is typically not serious and should go away over the next two to three days.

If you are worried about a delayed reaction, call 617-355-6117 and ask to speak with an allergy nurse.

When will I learn the test results?

The allergist or nurse tells you the results of the test before you leave. Your primary allergist will discuss the next step or the plan of care with you at a follow-up visit or on a telephone call with you.