Table 1. General recommendations for skin tests for drug allergy. From [2].

Test	Preparation/concentration	Reading
Patch test	Max. of 30% in petrolatum (preferred vehicle), alcohol, or aqua as the highest concentration (storage > 24 hours not recommended). Powder preparations: preferably in petrolatum (or in aqua), liquid preparations in aqua, steroid hormones in alcohol.	As in patch testing for contact allergens, final reading and evaluation after 72 hours. If necessary, additional reading after 20 minutes in immediate-type reactions.
Prick test	Ingredients and, if appropriate, additives should be tested separately. Testing with the pure agent is possible; down-titration if patient history is positive for severe reactions.	Evaluation: as with inhalant allergens Immediate (after 15 minutes): – positive if wheal > 3 mm and concomitant erythema and > negative control (NaCl) Late: palpable infiltration after 24 hours
Intradermal test	Only if prick test is negative; emergency preparedness Sterile preparation necessary Fresh preparation (< 2 h) Volume of injection 0.02 – 0.04 mL	Evaluation: no generally accepted standard Immediate (after 15 – 20 minutes): e.g., positive if wheal – increased by > 3 mm as compared to baseline – reaches 2 × the size of the control wheal – is > 8 mm or > 10 mm Late: palpable infiltration after 24 – 72 hours