Allergy to penicillin? Should we reconsider?

Penicillin is one of the best known antibiotics to the general public. What is not widely known is that the first penicillin used in the second world war is now almost useless due to the development of resistance from germs. Thus, synthetic derivatives of that first penicillin are used today. Antibiotics of this class are the cornerstone of the therapeutic quiver against germs.

Another well-known feature of penicillin is that it causes allergies. It is estimated that about 8% of people are allergic to it and consequently to its derivatives. What is not widespread is that most people who have a "known history of allergy to penicillin" are probably misled.

In 2 studies published last year, it was shown that among those who were assured by their doctors that they had an allergy to penicillin, only 5% had an actual allergy. This means that in Greece, while we assumed that around 800 000 of our fellow citizens have a penicillin allergy, in reality the number is close to 40 000.

But how did we end up with such big mistakes? Establishing a history of allergy to penicillin has always been based on the occurrence of symptoms consistent with the possibility of allergy, i.e. rash (redness) on the body, itch (scratching) of the skin, non-specific symptoms such as gastrointestinal disturbances, headaches or fainting spells, or more severe symptoms such as difficulty breathing and a drop in blood pressure (the so-called allergic shock). In fact, many times there are people who report unrecorded episodes in infancy or childhood that were classified as allergic reactions. Rarely or never has there been certification by performing specific tests for penicillin allergy, mainly because these are not widely available or because until a few years ago they were not commercially available.

But apart from the misunderstanding, the classification of a person as allergic to penicillin has further consequences. The first involves the use of second-line antibiotics (in the sense that they do not need to be used, not that they are not effective) that have a wider antimicrobial spectrum, are more expensive and have been associated with more complications. Also many times antibiotics with a structure similar to penicillin are not used, since there is a possibility of an allergy of about 10-15%. The second was shown in a study in which patients who were classified as allergic to penicillin, so they were forced to take other antibiotics when they had to be hospitalised, developed more infections subsequently from other more resistant microbes, needed more antibiotics and a longer hospital stay. And all of this also meant increased costs hospitalization.

In conclusion, a history of penicillin allergy should be confirmed by specific tests that are now available. And they are the only ones, since tests for allergies to other classes of antibiotics are not available on the market. One of the guidelines to doctors at a leading conference, after all, was: do not overuse other antibiotics in patients with a reported history of allergy to beta-lactams (the penicillin class) unless you confirm it.

Sources

www.medscape.com

www.pubmed.com

www.nejm.org

www.jwatch.org

Macy E, Ngor EW. Safely diagnosing clinically significant penicillin allergy

using only penicilloyl-poly-lysine, penicillin, and oral amoxicillin. J Allergy

Clin Immunol Pract. 2013 May-Jun;1(3):258-63

Macy E, Contreras R. Health care use and serious infection prevalence

associated with penicillin “allergy” in hospitalized patients: A cohort study. J

Allergy Clin Immunol. 2014 Mar;133(3):790-6.