Millions of people mistakenly think they’re allergic to penicillin

Oct. 11, 2023
Penicillin is one of the best antibiotics against potentially lethal infections, but many people mistakenly think they are allergic. Here’s a look at the symptoms of a true allergy and other details about penicillin.
Scott Froum, DDS, Editorial Director

September 28th marked the 95th anniversary of the discovery of penicillin. As one of the best antibiotics against potentially lethal infections, it is unfortunate that millions of people mistakenly think they have a penicillin allergy.

Approximately 10% of all US patients report having an allergic reaction to a penicillin. However, many patients who report penicillin allergies do not have true IgE-mediated reactions. When evaluated, less than 1% of the population is truly allergic to penicillin.1 Similarly, according to the Royal Pharmaceutical Society, although 6% of people in the UK have a penicillin allergy label on their medical record, 90% of those patients were found not to have an allergy when fully assessed.

Even patients who had a true penicillin allergy in the past may lose that allergy over their lifetime. Studies show that approximately 80% of patients with IgE-mediated penicillin allergy lose their sensitivity after 10 years.2

More about penicillin … Dental implant failure and penicillin allergy, explained

Cost of a mislabeled penicillin allergy

Being labeled allergic to penicillin is associated with a higher mortality rate of an extra six deaths per 1,000 patients in the year following treatment for infection. In addition, broad-spectrum antibiotics are often used as an alternative to penicillins. The use of broad-spectrum antibiotics in patients labeled “penicillin-allergic” is associated with higher health-care costs, an increased risk for antibiotic resistance, and suboptimal antibiotic therapy.

For example, a recent study of 838 patients receiving dental implants showed that those who had a “penicillin allergy” and were given another antibiotic during implant therapy had a failure rate more than twice that of patients without an allergy and given penicillin. An explanation of this increased failure rate is that penicillin and its derivatives are a superior choice for antibiotic coverage during dental implant procedures.3

Why do patients think they have penicillin allergies?

Many people believe they are allergic to penicillin for a variety of reasons, including:

  • Common side effects of antibiotics: Side effects such as nausea, gastrointestinal upset, cramps, bloating, headache, dizziness, and/or diarrhea are often confused with allergic reactions.
  • Symptoms of the infection being treated: A rash, for example, could be considered an allergic reaction and reported as such.
  • Allergy reported in the past: An allergy during childhood may disappear, but the perception of an allergy remains.
  • Parents told the patient they were allergic: Patients may have been told they were allergic to penicillin without proper testing.

What are the symptoms of a true penicillin allergy?

A true penicillin allergy is IgE-mediated and includes4:

  • Adverse reactions: reactions that occur immediately or usually within one hour of taking an antibiotic
  • Hives: multiple pink or red raised areas of skin that are intensely itchy
  • Angioedema: localized edema without hives affecting the abdomen, face, extremities, genitalia, oropharynx, or larynx
  • Breathing issues: wheezing and shortness of breath
  • Anaphylaxis: hypersensitivity (as to foreign proteins or drugs) resulting from sensitization following prior contact with the causative agent

What are the signs and symptoms of anaphylaxis?

Anaphylaxis is an acute allergic reaction that includes at least two of the following systems:

  • Skin: hives, flushing, itching, and/or angioedema
  • Respiratory: cough, nasal congestion, shortness of breath, chest tightness, wheeze, sensation of throat closure or choking, and/or change in voice quality (laryngeal edema)
  • Cardiovascular: hypotension, faintness, tachycardia (or less commonly, bradycardia), tunnel vision, chest pain, sense of impending doom, and/or loss of consciousness
  • Gastrointestinal: nausea, vomiting, abdominal cramping, and diarrhea

Editor’s note: This article originally appeared in Perio-Implant Advisory, a chairside resource for dentists and hygienists that focuses on periodontal- and implant-related issues. Read more articles and subscribe to the newsletter.


  1. Joint Task Force on Practice Parameters representing the American Academy of Allergy, Asthma and Immunology; American College of Allergy, Asthma and Immunology; Joint Council of Allergy, Asthma and Immunology. Drug allergy: an updated practice parameter. Ann Allergy Asthma Immunol. 2010;105(4):259-273. doi:10.1016/j.anai.2010.08.002
  2. Sampson HA, Muñoz-Furlong A, Campbell RL, et al. Second symposium on the definition and management of anaphylaxis: summary report—second National Institute of Allergy and Infectious Disease/Food Allergy and Anaphylaxis Network symposium. Ann Emerg Med. 2006;47(4):373-380. doi:10.1016/j.annemergmed.2006.01.018
  3. Zahra B, Nicholas B, Geoffrey R, Dina Z, Janal MN, Stuart F. Dental implant failure rates in patients with self-reported allergy to penicillin. Clin Implant Dent Relat Res. 2022;24(3):301-306. doi:10.1111/cid.13082
  4. Gonzalez-Estrada A, Radojicic C. Penicillin allergy: a practical guide for clinicians. Cleve Clin J Med. 2015;82(5):295-300. doi:10.3949/ccjm.82a.14111
Scott Froum, DDS, a graduate of the State University of New York, Stony Brook School of Dental Medicine, is a periodontist in private practice at 1110 2nd Avenue, Suite 305, New York City, New York. He is the editorial director of Perio-Implant Advisory and serves on the editorial advisory board of Dental Economics. Dr. Froum, a diplomate of both the American Academy of Periodontology and the American Academy of Osseointegration, is a volunteer professor in the postgraduate periodontal program at SUNY Stony Brook School of Dental Medicine. He is a PhD candidate in the field of functional and integrative nutrition. Contact him through his website at or (212) 751-8530.