• 4 Questions – S-3Ts
  • Symptoms
  • Tolerance of other beta-lactams
  • Time since reaction
  • Timing of reaction
    

Performing a comprehensive history is essential for proper evaluation of a patient with a reported penicillin allergy. There are no validated history questionnaires or uniformly accepted risk levels to date. Allergy history should incorporate the time course of the reaction as well as the description of the reaction.

The goal of the questions is to identify "low risk" penicillin allergy patients by eliminating high risk patients with immediate-type (IgE-mediated) reactions and severe T-cell mediated reactions or severe cutaneous adverse reactions (SCARS):

• AGEP – Acute generalized exanthematous pustules
• DRESS – Drug rash with eosirophilia and systemic symptoms
• SJS – Stevens-Johnson Syndrome
• TEN – Toxic epidermal necrolysis

Key questions in a drug allergy history include the following:

Question 1

• What were the symptoms?
  • rash – raised, pruritis
  • swelling – mouth, eyes, lips, tongue
  • blisters/ulcers
  • anaphylaxis symptoms

Question 2

• Has the patient tolerated beta-lactams since the initial reaction?
  • cephalexin
  • amoxacillin
  • IV beta-lactam

Question 3

• How long ago did the reaction occur – time since reaction?
  • < 1 yr
  • 2 – 5 yrs
  • > 10 yrs

** This question is most important for immediate type reactions (IgE-mediated) because patient may lose their sensitivity with time.

** 80% of patients with penicillin allergy become skin-test negative after 10 years and, therefore, lose their penicillin allergy.

Question 4

• What was the timing of the reaction after taking beta-lactam?
  • immediate (< 6 hrs)
    
  • delayed ( > 6 hrs)
  • unknown

Rapid onset of symptoms (within minutes to hours) distinguishes immediate from delayed reactions.