Is your child allergic to penicillin? What do you mean?

Penicillin is the most common cause of drug allergic side effects. About 10% of the population reports being allergic to penicillin. However, in a skin allergy test, only less than 20% of them give a positive reaction.

A description of the history of a possible allergic reaction to penicillin or another β-lactam antibiotic, of course, should be taken into account, but historical data alone is not enough to establish an accurate diagnosis of allergies. The importance of penicillin in the treatment of certain infections in children and the chemical similarity of penicillin with other β-lactams (amoxicillin, cephalosporins) make the diagnosis of penicillin allergy accurate in children very important. This is all the more relevant as no commercial skin allergen (Pre-Pen) is currently available to detect IgE-induced reactions to penicillin.

Fortunately, the risk of an anaphylactic reaction to penicillin is low and amounts to 0.01-0.05% for each antibiotic cycle. Non-anaphylactic-type allergic reactions, characterized by a maculopapular rash, arthralgia or vomiting, are more common. Sometimes parents say their child is allergic to penicillin, which is manifested by vague or unusual anaphylactic reactions. It may be a rash that appears a few days after treatment with amoxicillin / clavulanate, and, with more detailed questioning, it turns out that the rash was not generalized , there were no hives and general symptoms that could indicate a type of anaphylactic reaction. Should the attending physician avoid prescribing β-lactam antibiotics to the child?

The best way to detect hypersensitivity to penicillin is to organize a skin allergy test. But to date, the Pre-Pen test is not available. In addition, it only detected allergies to the main determinant (penicilloyl polylysine), which is the main metabolite of penicillin, while the minor determinants are responsible for 20% of penicillin anaphylaxis and the test. Pre-Pen in these cases. case a negative result. A commercial test with minor determinants has never existed, but a dilute solution of benzylpenicillin can serve as a substitute. The allergic skin test does not at the same time predict the development of allergic reactions of other types, which may manifest as glomerulonephritis, vasculitis, hemolytic anemia, erythema multiforme and Stevens-Johnson syndrome. These reactions are not predictable.

Amoxicillin and ampicillin can cause the development of a maculopapular rash, which is not the result of an anaphylactic reaction, and occurs in 5-10% of patients. An indication in the history of such a rash does not require a skin test. But in children who have a history of developing hives with penicillin, a skin test should be done.

Patients with an anaphylactic reaction to penicillin tend to cross-react with other β-lactam antibiotics. The risk of developing an allergic reaction to cephalosporins with a positive penicillin skin test is 2%. If a child suspected of an anaphylactic reaction to penicillin requires the administration of cephalosporins, a penicillin skin test should be performed. If the result is positive, the cephalosporins should be discarded.

It is impossible to exclude an anaphylactic reaction solely on the basis of anamnesis, which even indicates a reaction mechanism not mediated by IgE, since 12.5 to 33% of these patients give a positive skin test. At the same time, more than 25% of patients with anamnestic data indicating a type of anaphylactic reaction show a negative result on a skin test.

Thus, the most reliable data on the presence of allergies can be obtained by performing a skin allergy test. If the result of a correctly performed test is negative, the use of penicillin is safe in 97 to 99% of patients. It is hoped that in the near future, commercial production of an allergen will be launched, containing both major and minor determinants. But will it be necessary to do a test for all patients with a history of allergy? It will likely be indicated for children with conditions in which penicillin is the best or only appropriate treatment. Screening is also indicated for young children with frequent infections (for example, episodes of acute otitis media), as alternative drugs (macrolides, azalides) are less active against a number of important pathogens than l amoxicillin.