Allergic to Penicillin?

PenicillinAdverse reactions to medications are very common.  Among the drugs associated with immediate hypersensitivity reactions (i.e., Type I allergy, IgE antibody-mediated allergy), penicillins are the most commonly observed.

Penicillin allergy is reported in approximately 7 to 10% of community populations and up to 20% of hospitalized patients.  What is amazing is that more than 90% of these patients do not actually have true penicillin allergy!

There are three common causes for this high rate of false positive penicillin allergy reports:

  1. Mislabeling of a side effect (e.g., gastrointestinal upset) as an “allergy”
  2. Coincidental event (e.g., headache or rash due to an underlying infection)
  3. Loss of true allergy sensitivity over time with avoidance of penicillins.

Penicillin allergy can be ruled out with the help of a standardized testing procedure which is routinely done in our office at Black & Kletz Allergy.  Skin testing was introduced as a diagnostic intervention for the evaluation and management of patients with a history of penicillin allergy in 1960’s.  This procedure is commonly performed with minimal risk.  Penicillin skin testing can be done safely in properly selected patients with suspected penicillin allergy and can even be performed in pregnant women with Streptococcal infections.

The procedure for testing involves three stages:

  1. Skin prick testing with a small amount of diluted penicillin “antigens” (commercially prepared testing reagents) with negative and positive controls.
  2. If the prick tests are negative after 20 minutes, a tiny quantity of the antigen in injected into the superficial layers of the skin (i.e., intradermal skin test).
  3. If the intradermal skin test in in this second stage is also negative after 20 minutes, the patient will be given 250 mg. of amoxicillin by mouth (i.e., oral challenge) and will be closely monitored for 90 minutes.

If the patient tolerates all three stages without any adverse effects, the patient may receive penicillins if needed, without increased risk of immediate allergic reactions.  The negative predictive value of penicillin allergy testing is more than 99%.

Penicillin allergy testing should be performed in a healthcare setting only by clinicians with the knowledge, training, and experience to select appropriate patients for this procedure, interpret test results, and manage a systemic allergic reaction should it occur.

Unverified penicillin allergy in hospitalized patients is associated with longer hospital stays and increased rates of serious drug-resistant infections.  The alternative antibiotics to penicillin can be associated with higher cost and/or greater risk for untoward side effects.

For this reason, the “Choosing Wisely” program of the American Board of Internal Medicine Foundation recommended in 2014 that clinicians not overuse non-penicillin antibiotics in patients with a history of penicillin allergy, without an appropriate evaluation.  The National Quality Partners’ Antibiotic Stewardship Action Team recommends penicillin allergy skin testing as a component of a comprehensive antibiotic stewardship program.

Penicillin allergy testing is associated with an unrealized potential:  this procedure can accurately identify the approximately 9 of 10 patients who despite reporting a history of penicillin allergy can receive penicillins safely.

On the basis of current evidence, the American Academy of Allergy, Asthma and Immunology (AAAAI) believes that more frequent and routine performance of penicillin allergy testing will result in reduced costs of care, enhanced patient safety, and improved outcomes.

The board certified allergy doctors at Black & Kletz Allergy have been performing penicillin skin testing routinely for many years on both adults and children.  Black &Kletz Allergy has 3 convenient locations in the Washington, DC, Northern Virginia, and Maryland metropolitan area.  We have offices in Washington, DC, McLean, VA (Tysons Corner, VA), and Manassas, VA which all offer on-site parking.  The Washington, DC and McLean, VA locations are Metro accessible and there is a free shuttle that runs between the McLean, VA office and the Spring Hill metro station on the silver line.  Please call us to make an appointment or you can click Request an Appointment and we will reply within 24 hours by the next business day.  The allergists of Black & Kletz Allergy are eager to help you with your allergy, asthma, sinus, and immunology needs.  We are dedicated to providing excellent care and service to you as we have been doing in the Washington, DC metro area for more than 5 decades.