Drug allergy

What is a drug allergy?

Drug allergies are the immune system’s response to certain drugs. The immune system mistakenly sees drugs or medication as harmful invaders. The body responds with certain chemicals and releases large amounts of histamine to destroy the invaders, causing symptoms such as a skin rash or nausea.

What are the signs of a drug allergy?

Symptoms of drug allergies can often be confused with the side effects of the drugs themselves but an allergic reaction can cause symptoms such as the following:

  • Hives
  • Itching of the skin and eyes
  • Skin rash
  • Swelling of the lips, tongue and face
  • Congestion

Sometimes if the allergy is more aggressive it can cause anaphylaxis, which causes shortness of breath, blueness of the skin, symptoms of urgency, abdominal pain, confusion, diarrhoea, dizziness, fainting and palpitations.


How can drug allergies be diagnosed?

To diagnose a drug allergy, your doctor will need to know about your medical history and will examine your symptoms. A skin test can be used to test for an allergy to penicillin.

However, if you have had a very bad reaction to a certain drug, your doctor will simply rule out that drug and have you avoid that specific drug in the future.


What causes drug allergies?

Drug allergies are caused when the body’s immune system reacts badly to certain drugs. The most common drug allergies are to penicillin and antibiotics. Other drugs that people are allergic to include, sulfa drugs, barbiturates and anti-seizure medications.


What to do if you have a drug allergy

The first step is to control the symptoms, which involves using antihistamines or corticosteroids to control symptoms like a rash, hives and itching. Bronchodilators may be prescribed to widen the airways and can be used for coughing and lung congestion. If someone experiences anaphylaxis, they may need a shot of epinephrine and will need immediate emergency care.


Desensitisation can be used in the future to treat allergies that people have to certain drugs. This involves being exposed to tiny amounts of penicillin, for example and increasing the dosage as your body becomes more desensitised to the drug and handles it better. This is only necessary if there is no other drug to treat your health problem.


If you have a drug allergy, it’s a good idea to carry a card or wear a bracelet of a tag to specify what allergies you have in case of an emergency.

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