Penicillin "Allergy" Label at Hospital Admission May Lead to 10% Longer Hospital Stays and More Serious Antibiotic Resistant Infections

But 19 in 20 patients with a history of penicillin "allergy" are not penicillin allergic

Mar 10, 2014, 09:10 ET from ALK

ROUND ROCK, Texas, March 10, 2014 /PRNewswire/ -- A new study in the Journal of Allergy and Clinical Immunology, funded by ALK, finds that a penicillin "allergy" label adversely affects the quantity and quality of health care in hospitalized patients.  The penicillin allergy label is the most common drug "allergy" listed in medical records during hospital admissions.  Analyzing Kaiser Foundation hospitals' patient records over a 3-year period, the study found that about 11% of those admitted carried a penicillin "allergy" label.  "Healthcare use and serious infection prevalence in associated with penicillin allergy in hospitalized patients: A cohort study" by Eric Macy, MD and Richard Contreras, MS is published in the March, 2014 edition. The largest study of its kind, it looked at over 51,000 patients admitted to Kaiser Foundation hospitals in Southern California from 2010 through 2012. 

"It is important to know if you are allergic to penicillin," said Eric Macy, MD. "This medical history detail impacts not only critical health care decisions, but it greatly impacts cost." said Eric Macy, MD.  "In the hospital setting we found this translates to about 10% more hospital days and significantly more Clostridium difficile, Methicillin-resistant Staphylococcus aureus (MRSA), and vancomycin resistant enterococcus (VRE) infections.  These adverse events occur because penicillin "allergic" patients are given more broad spectrum antibiotics, including ciprofloxacin, vancomycin, clindamycin, and third or greater generation cephalosporins.  Previous work by our group has shown than less than 5% of individuals who carry a history of penicillin "allergy" are truly allergic."


A penicillin "allergy" history, although often inaccurate, is not a benign finding at hospital admission. Subjects with a penicillin "allergy" history spend significantly more time in the hospital. These subjects are also exposed to greater risk of infection and significantly more antibiotics previously associated with C difficile and VRE.

It is estimated that of the 30 million US patients reporting as penicillin allergic, 28.5 million actually are not. That means up to 19 out of 20 patients who think they are allergic to penicillin are misinformed1,2.   Numerous medical publications and medical professionals have written about this common misdiagnosis. This over-reporting of penicillin allergy may lead to higher medical costs for both patients and the healthcare systems3. Antibiotic costs for patients reporting penicillin allergies are up to 63% higher4. In addition to cost savings, improved patient care and combatting drug-resistant bacteria are other reasons why testing for a penicillin allergy may be so important.

About ALK
ALK is a research driven, global pharmaceutical company focusing on allergy treatment, prevention and diagnosis. As the world leader in allergy immunotherapy, a treatment given to increase immunity to substances causing allergic symptoms, ALK is devoted to improving the quality of life for people with allergies by creating products that treat the cause of allergies. ALK is also committed to supporting the business of allergy by providing diagnostic tools, automation software and customized business, technical and clinical consulting services.


PRE-PEN is indicated for the assessment of sensitization to penicillin (benzylpenicillin or penicillin G) in patients suspected to have clinical penicillin hypersensitivity. A negative skin test to PRE-PEN is associated with an incidence of immediate allergic reactions of less than 5% after the administration of therapeutic penicillin, whereas the incidence may be more than 50% in a history-positive patient with a positive skin test to PRE-PEN.

These allergic reactions are predominantly dermatologic. Whether a negative skin test to PRE-PEN predicts a lower risk of anaphylaxis is not established. Similarly, when deciding the risk of proposed penicillin treatment, there are not enough data at present to permit relative weighing in individual cases of a history of clinical penicillin hypersensitivity as compared to positive skin tests to PRE-PEN and/or minor penicillin determinants.

PRE-PEN is contraindicated in those patients who have exhibited either a systemic or marked local reaction to its previous administration. Patients known to be extremely hypersensitive to penicillin should not be skin tested.

The risk of sensitization to repeated skin testing with PRE-PEN is not established. Rarely, a systemic allergic reaction including anaphylaxis (see below) may follow a skin test with PRE-PEN. To decrease the risk of a systemic allergic reaction, puncture skin testing should be performed first. Intradermal skin testing should be performed only if the puncture test is entirely negative.

  1. Salkind, Alan, R. et all. Is This Patient Allergic to Penicillin? JAMA, May 16, 2001 - Vol. 285, No. 19
  2. Macy E, Ngor E. Safely diagnosing clinically significant penicillin allergy using only penicilloyl-poly-lysine, penicillin and           oral amoxicillin. J Allergy Clin Immunol: In Practice 2013;1:258-63.
  3. Arroliga, Mercedes, Pien, Liliy. Penicillin Allergy: Consider Trying Penicillin Again. Cleveland Clinic Journal of Medicine. Volume 70. Number 4. April 2003
  4. Park, Miguel. Mayo Clinic Proc. March 2005;80(3):405-410

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