16% of children with a history of penicillin allergy may be missed if amoxicillin skin test not done


Penicillin skin testing is an effective tool for determining penicillin allergy. The standard skin test panel at Mayo Clinic included benzylpenicillin polylysine, penicillin G, and benzylpenicilloate.

Amoxicillin should be considered part of the penicillin skin test panel when testing children, according to a new study.

The majority of the children (90%) had a negative penicillin skin test, 9% had a positive penicillin skin test, and 1% had an equivocal result.

Of children who had a positive skin test:

- 47% were positive to benzylpenicillin polylysine
- 29% were positive to penicillin G
- 35% were positive to benzylpenicilloate

Penicillin skin testing is still very useful and is the most important component in the evaluation of penicillin allergy. However, 16% of children with a history of penicillin allergy, especially to amoxicillin, may be missed if an amoxicillin skin test is not included with the other components of the penicillin skin test.

If the children have a reaction to amoxicillin specifically and the penicillin skin test and amoxicillin skin test are negative, an amoxicillin challenge should be under medical supervision.

If someone is not allergic to the penicillin, but is responding to amoxicillin, it would indicate that the beta lactam "backbone" is not what they're allergic to - they are allergic to the side chain of one of the penicillin derivatives. In this case many other cephalosporins or beta lactams may be used.



Hypersensitivity reactions to beta-lactam antibiotics: MAUS mnemonic 20-20-40-20%. Click here to enlarge the image.

References:

Kids More Likely to Show Allergy to Amoxicillin Than Adults. Medscape.

Diagnosis of Immediate Hypersensitivity to β-Lactam Antibiotics Can Be Made Safely with Current Approaches. Int Arch Allergy Immunol. 2011 Nov 1;157(3):311-317.

Penicillin and Cephalosporin allergy - Annals of Allergy, Asthma & Immunology, 2014 http://buff.ly/1ltZntr

Testing for penicillin allergy can be done at any age. Consider testing with PrePen, Penicillin G and ampicillin. AAAAI Ask the Expert, 2012.

Outcomes in the Use of Cephalosporins in Pediatric Patients with a History of Penicillin Allergy http://goo.gl/0HGo4

Image source: Penicillin nucleus, Wikipedia, GNU Free Documentation License.

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