Penicillin allergy

  1. Incidence of self-reported penicillin allergy ranges from 1-10%.

Frequency of life-threatening anaphylaxis estimated at .01-.05%.

Estimated 32 million people in the US have documented penicillin allergy.

Penicillin is the most common drug allergy in medical records with the prevalence of 6 to 25%.

Benign cutaneous reactions such as  urticaria and delayed maculopapular exanthema are the most common type of reactions.

  • Penicillins are associated with other severe cutaneous reactions, such as drug reaction with the eosinophilia and systemic symptoms (DRESS) and the Stevens-Johnson syndrome and toxic epidermal necrolysis.

The rate of positive penicillin skin tests have decreased over the last decades.

The mean interval between the administration of penicillin and the onset of symptoms with anaphylaxis is less than 15 minutes in 85% of cases and most patients die with in one hour after administration.

Only 10-20% of patients reporting a history of penicillin allergy are truly allergic when assessed by skin testing.

Penicillins are the most common cause of drug induced fatal and nonfatal and anaphylaxis.

Aminopenicillins are among the highest risk drugs that cause benign delayed examthems which commonly occur  in the context of acute Epstein-Barr virus infection. 

More than 80% of patients with self-reported history of penicillin allergy have no evidence of IgE antibodies to penicillin.

Around 80% of patients with demonstrable immunoglobulin E-mediated hypersensitivity will lose their allergy altogether within 10 years of avoiding penicillin.

Virtually all patients with negative skin testing can take penicillin without serious sequelae.

More than 95% of patients labeled is having penicillin allergy ultimately are able to tolerate the penicillin class of drugs.

Most patients labeled with penicillin allergy did not undergo any evaluation to determine the accuracy or persistence of the allergy.

Frequency of all adverse reactions to penicillin in the general population ranges from 0.7 to 10%.

Benign cutaneous reactions such as urticaria and delayed maculopapular exanthema are the most common types of reactions.

Type I reactions, or immediate are often associated with systemic manifestations of anaphylaxis.

Anaphylaxis reactions occur in about 0.004% to 0.015% of penicillin courses and are most commonly seen in adults between the ages of 20 and 49 years.

Penicillins are the most common cause of drug induced fatal and non-fatal anaphylaxis in the US.

The lowest rate of anaphylaxis is for oral penicillins.

Aminopenicillins are among the highest risk drugs that cause benign delayed exanthems, which commonly occur in the context of acute Epstein-Barr virus infection.

Penicillin seven associated with other severe cutaneous reactions such as the DRESS syndrome and the Stevens-Johnson syndrome and toxic epidermal necrolysis.

Anaphylaxis can be induced by exposure with oral, subcutaneous and intravenous administration of penicillin.

In a study that included within 65,000 patients with a history of of penicillin.penicillin allergy who received more than 127,000 courses of cephalosporins, only three cases of anaphylaxis were associated with the drugs: this is not statistically different from anaphylactic rates and non penicillin allergic patients who receive cephalosporins.

No more than 2% of patients with a positive reaction to penicillin skin tests have a reaction to cephalosporins, with the exception of patients who are allergic to aminopenicillins but not to benzopenicillin, penicillin VK and other penicillins.

Divided into IgE-mediated (immediate type) vs non IgE mediated hypersensitivity reactions.

IgE mediated reactions include anaphylaxis, urticaria, angioedema, and bronchospasm.

IgE reactions generally occur within minutes of exposure the drug but can delayed up to 72 hours.

Non IgE mediated allergic reactions include hemolysis, thrombocytopenia, interstitial nephritis, serum sickness, Stevens-Johnson syndrome, drug fever, erythema multiforme and toxic epidermal necrolysis.

Non IgE mediated adverse drug reactions generally occur 72 hours after drug exposure.

Patients who experience a true allergy reaction have about an 80% chance of losing their sensitivity to penicillin within 10 years.

Once an individual is labeled as having a penicillin allergy it is subsequently rarely questioned, increasing a patient’s risk of receiving sub optimal antibiotic therapy.

Many patients assume that they must be allergic to penicillin because a parent or sibling is.

Patients labeled as allergic to penicillin have a 69% greater risk of methicillin resistant Staphylococus aureus and a 26% greater risk of Clostridium difficile than people with the same age and sex who are not labeled allergic to the drug.

Increased use of broad spectrum non-beta-lactam antibiotics instead of non beta-lactam options account for a large portion of the increased risk in patients labeled allergic.

Patients with reported penicillin allergy are more likely to receive an unecessarily broad-spectrum and less appropriate antibiotic  treatments which may be less effective, more toxic and more expensive than penicillins.
Patients with a reported penicillin allergy have higher rates of C. difficile colitis, MRSA, , and vancomycin resistant enterococcus infections compared with matchEd controls.
Penicillin allergy labeling is associated with higher drug costs, more frequent healthcare complications, longer hospital stays and increased surgical site infections.

Patients undergoing surgery with a history of penicillin allergy receive suboptimal beta-lactam alternatives prophylactically, which can prolong operations and raise the risk of surgical site infections, accounting for 40% of all healthcare associated infections among hospitalized patients.

In patients reporting a penicillin allergy there was a 51% increase in the risk of developing a surgical site infection, attributable to inferior antibiotic prophylactic therapy.

Drug challenges with penicillin is the standard for assessing tolerance of the drug. 

Increasing amounts of the drug are administered over time and the current negative predictive value is estimated approximately 98%, with a 2-3% false rate of negative reactions after penicillin challenge, and generally mild cutaneous reactions.

Skin testing with penicilloyl polylysine is the most common reagent used to assess penicillin allergy.

The natural history of IgE mediated penicillin allergy reveals a loss of such allergic phenomenon overtime.

Patients labeled with penicillin allergy have increased rates of MRSA , and Clostridioides difficile and surgical site infections.

A label of penicillin algae is related to higher healthcare costs.

It is estimated at 90% of patients labeled as allergic to penicillin can safely receive the drug.

The majority of adults with a penicillin allergy label can have the label removed.

Protocols exist for rapid desensitization of penicillin with oral and intravenous measures.


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