Allergic reactions to medications

Many prescription and nonprescription medications can cause an allergic reaction. The seriousness of the allergic reaction caused by a certain medication will vary.

Respiratory reactions to a drug allergy can include:

• A severe allergic reaction (anaphylaxis).
• Wheezing.
• Worsening of asthma.

Having a medication allergy affects your ability to take that medication in the future, and it often means that you cannot take the medication again. An allergic reaction may mean you will not be able to take medications that have a similar chemical makeup; this applies to many antibiotics and local anesthetics as well as other families of medications.

Medications that may cause an allergic reaction are:

• Insulin.
• Antibiotics, such as penicillin, cephalosporins, or sulfonamides.
• Vaccines.
• Anticonvulsants, barbiturates, or local anesthetics.
• Contrast dyes used in X-ray studies.
• Blood products.
• Certain enzymes, such as trypsin and streptokinase.

If you suspect an allergic reaction:

• Call the health professional who prescribed the medication before taking your next dose. This helps determine whether you should stop taking the medication or take a different one.
• From a nonprescription medication, stop taking the medication. If you feel you need to continue taking the medication, call your health professional.