Do I need to have skin tests for all antibiotics?

Skin Testing for Antibiotics: When Is It Necessary?

Skin testing is not necessary for all antibiotics and should only be performed in specific clinical scenarios, particularly for patients with a history of anaphylaxis or recent suspected IgE-mediated reactions to penicillins. 1

When Skin Testing IS Needed

• Skin testing is recommended for patients with a history of anaphylaxis or recent reactions suspected to be IgE-mediated to penicillins 1
• Patients with a history of anaphylaxis to cephalosporins should undergo penicillin skin testing and drug challenge prior to administration of penicillin therapy 1
• Skin testing may be advisable for specific patients with multiple drug allergies due to the possibility of coexisting sensitivities to different beta-lactam antibiotics 1

When Skin Testing is NOT Needed

• Skin testing is not indicated for patients with reaction histories inconsistent with allergy (such as headache, isolated gastrointestinal symptoms, or family history of penicillin allergy) 1
• For patients with histories inconsistent with allergy but who are anxious, a single-dose amoxicillin challenge is sufficient without prior skin testing 1
• Patients with a history of penicillin or cephalosporin allergy can receive carbapenems without prior testing or additional precautions 1
• Aztreonam may be administered without prior testing to patients with penicillin or cephalosporin allergy, unless there is a history of ceftazidime allergy 1
• Skin testing is not needed for non-IgE-mediated reactions or nonallergic adverse reactions 1, 2

Cross-Reactivity Considerations

• The risk of cross-reactivity between penicillins and cephalosporins with dissimilar side chains is very low (approximately 0.1%) 1
• For patients with any immediate penicillin allergy history, a non-cross-reactive cephalosporin can be administered by full dose or drug challenge without prior testing 1
• Clinical cross-reactivity between carbapenems and other beta-lactams is low, with studies showing risk of cross-reactivity as 0.87% (95% CI: 0.32%-2.32%) 1
• There is no cross-reactivity between penicillin and aztreonam for IgE- or T-cell-mediated hypersensitivity, except when there is a history of ceftazidime allergy (due to shared R1 side chain) 1

Skin Testing Procedure and Reliability

• Penicillin skin testing should only be performed by personnel trained in application and interpretation, with preparedness to treat rare anaphylaxis 1
• The negative predictive value of penicillin skin testing is >95%, making it reliable for ruling out IgE-mediated allergies 1, 3
• Penicillin skin testing is more reliable than in vitro tests for evaluating IgE-mediated penicillin allergy 1
• A positive test is defined by a wheal 3 mm or greater than the negative control for either prick/puncture or intradermal tests, accompanied by a 5 mm or greater flare 1

Alternative Approaches

• For low-risk patients, direct oral amoxicillin challenges are safe and effective for penicillin allergy delabeling without prior skin testing 1, 4
• Inpatient-based penicillin skin testing programs have been shown to improve antibiotic stewardship, with 95-98% of patients testing negative 1
• Implementation of beta-lactam allergy pathways in healthcare systems can improve antibiotic stewardship outcomes 1

Pitfalls and Caveats

• The practice of skin testing prior to antibiotic administration in the absence of a history of allergy has no scientific basis and is not recommended 2
• Giving a "test dose" prior to administration of antibiotics has no scientific basis and does not protect patients from anaphylactic reactions 2
• The sensitivity of penicillin skin tests decreases over time - 93% are skin-test positive 7-12 months after reactions, but only 22% are positive 10 or more years after reactions 3
• Skin testing is not indicated for clearly non-IgE-mediated reactions or nonallergic adverse reactions 1

In conclusion, routine skin testing for all antibiotics is unnecessary and should be reserved for specific clinical scenarios, particularly for patients with histories of anaphylaxis or recent suspected IgE-mediated reactions to penicillins.