Risk factors for developing drug allergies include past drug allergy, genetic factors, recurrent drug exposure, and certain diseases. Overall, objective testing for the diagnosis of drug allergy is limited. Skin testing is helpful for some medications that cause immediate hypersensitivity reactions, although skin testing has been fully validated only for penicillin. 

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Allergy to a drug can be excluded by performing a graded challenge. Graded challenge does not modify the allergic response to the drug or prevent recurrent reactions. Thus, challenges must be performed with caution and in a monitored setting, and patients who tolerate drug challenges prove that they are not allergic to that medication. 

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Desensitization is a procedure that alters the immune response to the drug and results in temporary tolerance, allowing the patient with a drug hypersensitivity reaction to receive an uninterrupted course of the medication safely. Once the medication is discontinued or if treatment is interrupted for a sufficient period of time, the patient's hypersensitivity to the medication returns. Desensitization is only safe and effective for certain types of drug allergy.