Drug Allergies: Knowing How to Recognize and Respond

drug allergy pills
Medications can cause unwanted side effects – or allergies. While many people experience side effects (listed on the drug label), drug allergies account for less than 10 percent of adverse reactions. Like other allergic reactions, drug allergies occur when the immune system malfunctions, in this case by interpreting a medicine as a foreign invader and launching an attack against it. The attack then sets off a chain reaction that leads to symptoms ranging from mild to life-threatening.

Common Drug Allergies and Symptoms

Certain medicines trigger allergic reactions more than others. Penicillin and similar antibiotics are the most common, with other allergy-causing drugs including:
  • analgesics (painkillers)
  • anticonvulsants (used to treat epilepsy and bipolar disorder)
  • insulin, particularly from an animal
  • iodine (used in x-rays dyes)
  • sulfa drugs (another form of antibiotics).

Drug allergies can cause various symptoms, depending on your level of exposure and whether you received the drug by injection, pill or as an ointment. The presence of histamine (proteins released by your immune system during an allergic reaction) can bring about skin irritations, such as:

  • hives (itchy, red welts)
  • itchy skin
  • photoallergy (a rash caused by sun exposure)
  • rashes.

While most allergic reactions occur immediately after the allergen exposure, drugs can take days or even weeks to trigger a reaction. The exception is a less common and more severe allergic reaction known as anaphylaxis. This potentially life-threatening condition requires immediate medical attention, often resulting in an injection of epinephrine (adrenaline). Symptoms of anaphylaxis include:

  • abdominal pain or cramps
  • angioedema (swelling of the eyes, lips, tongue and hands)
  • anxiety
  • bluish discoloration of the skin
  • confusion
  • diarrhea
  • fainting or light-headedness
  • hives in different parts of the body
  • irregular or rapid heartbeat
  • vomiting
  • wheezing or difficulty breathing.

Determining an Allergic Reaction

Drug allergies can be difficult to diagnose since reactions tend to occur days or weeks after exposure. Still, if you experience an adverse reaction, call your doctor – and do not stop taking your prescription without consent from your healthcare provider.
 
During the initial conversation, your doctor will ask questions about your symptoms, current and past medications, medical history and known allergies. A physical exam may follow, during which your doctor may administer a skin test to confirm whether you have an allergy. Not available for all drugs, skin tests are unadvisable – and dangerous - if you've experienced a severe reaction. In that case, your doctor may simply take you off the drug and alter your treatment plan.
 
Sometimes a doctor will take a blood sample to look for antibodies linked to certain drugs. These samples might also reveal the presence of blood-borne markers, which indicate an immune system response and point the finger at an allergy.
 
If your doctor determines that you do have an allergy, you can discuss treatment plans, which may involve:
  • antihistamines
  • avoiding the drug
  • bronchodilators to open the airways
  • changing your form of treatment
  • corticosteroids to stop the itching
  • immunotherapy (used occasionally with penicillin and administered by an allergist)
  • wearing an ID bracelet or pendant (MedicAlert) or carrying a card specifying your drug allergy.
Remember, if you experience an adverse reaction to a drug, seek advice from your healthcare provider. Drug allergies are serious and warrant a doctor's attention. Obtaining a proper diagnosis can save your life.
 
Resources
 
Accetta, D. (2007). Medical encyclopedia: Drug allergies. Retrieved March 14, 2009, from the Medline Plus Web site: http://www.nlm.nih.gov/medlineplus/ency/article/000819.htm.
 
Keim, S. (2009). Drug allergy. Retrieved March 14, 2009, from the eMedicine Health Web site: http://www.emedicinehealth.com/drug_allergy/article_em.htm.
 
Mayo Clinic. (1998-2009). Drug allergy: Watching for unexpected reactions to medications. Retrieved March 14, 2009, from the Mayo Clinic Web site: http://www.mayoclinic.com/print/drug-allergy/HQ00582/METHOD=print.
 
Medicine Net (2007). Drug allergies. Retrieved March 14, 2009, from the Medicine Net Web site: http://www.medicinenet.com/drug_allergies/article.htm.