HF 8224

Penicillin Allergy Evaluation in Pregnancy

Penicillin is the preferred treatment for infections during pregnancy. It is used to:

  • Prevent Group B Strep infections in infants and mothers (1 in 3 women have Group B Strep).

  • Prevent surgical site infections during C sections (1 in 5 births).

  • Treat prolonged rupture of membranes and fever during the birth.

About 1 in 10 women have a penicillin allergy listed in their health record. When this type of allergy is listed, doctors often choose other antibiotics. The other medicine may not work as well and could lead to complications or a long hospital stay.

Why do I need penicillin testing?

It can help figure out if it is safe for you to use penicillin and other related medicines. Most of the patients who are tested are cleared to safely use penicillin again.

Who needs penicillin allergy evaluation?

  • Low risk – Patients who only had nausea, diarrhea, vomiting or headache do not need testing. They can safely use penicillin.

  • Moderate risk – Patients who had hives, swelling or rash will be referred for an Allergy consult.

  • High risk – Patients who had severe skin reactions such as Stevens Johnson syndrome or DRESS, or anaphylaxis will not be referred for an allergy consult. Instead, other antibiotics would be used.

How does penicillin allergy testing work?

This is a two-step process that takes about 2-3 hours. The type of testing will depend on your past penicillin reaction.

Step 1: You will first have a skin test. This may start with a skin scratch test. Then, you may have the medicine placed just under the skin using tiny needles. The test is very safe and fairly painless.

Step 2: After a negative skin test, you will be given two doses of oral amoxicillin over about 60-90 minutes as a “challenge.” This is to prove you can take it safely. We will monitor you during this time.

Is penicillin testing safe?

Recent studies show this is a safe test during pregnancy.

How do I prepare for the test?

Do not take antihistamines for 7 days before the test. This is very important. This means you should not take any allergy pills, cold medicines, etc. in the 7 days before your test. These include:

  • Benadryl®

  • Claritin®

  • Zyrtec®

  • Any other medicines with antihistamines

What happens after the test?

A negative skin test and challenge makes future reactions very unlikely. The warning about penicillin allergy will be removed from your health record. Your doctors will be told that you can safely use penicillin again in the future. Negative testing alone cannot guarantee that you will not have a future reaction, like a rash. Though, rashes are less likely after a negative test.

When should I be tested?

It is best to be tested before getting pregnant. But you can also have the test any time during your pregnancy.

How can I get an appointment for testing?

Talk to your doctor. Your doctor can place a consult to get the process started.

Who to Call

Call if you have any questions about this test.

UW West Allergy clinic

(608) 263-6180 or (800) 323-8942

UW 20 S. Park Allergy clinic

(608) 287-2600 or (888) 703-2778

UW East Allergy clinic

(608) 265-1280 or (800) 323-8942