Drug Allergy

What is a drug allergy

A drug allergy is the abnormal reaction of your immune system to a medication. Any medication — over-the-counter, prescription or herbal — is capable of inducing a drug allergy. However, a drug allergy is more likely with certain medications.

A drug allergy is not the same as a drug side effect, a known possible reaction listed on a drug label. A drug allergy is also different from drug toxicity caused by an overdose of medication. There are many ways in which people can react to drugs and medicines but not all of these are allergy related, which can cause confusion. Some people are genuinely allergic to certain drugs, but this is quite rare. Most drug ‘reactions’ are due to the various issues described below.

Symptoms of a drug allergy

Signs and symptoms of a serious drug allergy often occur within an hour after taking a drug. Other reactions, particularly rashes, can occur hours, days or weeks later.

Drug allergy signs and symptoms may include:

• Rashes
• Itching
• Nausea
• Vomiting
• Diarrhoea (or occasionally constipation)
• Lethargy
• Headaches
• Blurred vision

All the known side effects from a drug are listed in the patient information guide that comes with the drug. These are listed in order of frequency (the most common will be first on the list).

Anaphylaxis from a drug allergy

Anaphylaxis is a rare, life-threatening reaction to a drug allergy that causes the widespread dysfunction of body systems. Signs and symptoms of anaphylaxis include:

• Tightening of the airways and throat, causing trouble breathing
• Nausea or abdominal cramps
• Vomiting or diarrhea
• Dizziness or lightheadedness
• Weak, rapid pulse
• Drop in blood pressure
• Seizure
• Loss of consciousness

Read more about anaphylaxis

How can I manage my drug allergy?

If you are allergic to a drug, it is important to make sure everyone knows. Health services are sometimes not very good at communicating this information or sharing it with other services or even looking at it when it is recorded. Here are 5 top tips to help you:

1. Always ask whether the allergy has been recorded in your notes.
2. Volunteer the information to everyone who is involved in your care, even if they don’t ask.
3. Make sure you are given an allergy bracelet when you are in hospital.
4. If your allergy is severe, consider wearing your own allergy bracelet.
5. If you are given drugs to take at home, always read the label and information leaflet very carefully.

For more detailed information about drug allergy and the range of different allergy medications please find further useful resources below.

When to see a health care professional

Call 999 or emergency medical help if you experience signs of a severe reaction or suspected anaphylaxis after taking a medication.

If you have milder symptoms of a drug allergy, see your doctor as soon as possible.

Aspirin is one of the oldest medicines known, and is common in many traditional medicine remedies including Chinese medicines. Aspirin was originally extracted from plants but is now made synthetically. A number of similar medicines have now been produced, and this group of medicines is known as Non-Steroidal Anti-Inflammatory Drugs or NSAIDs. Other NSAIDs are naproxen and ibuprofen (Nurofen).

NSAIDs can be very effective medicines for pain and fever. They work by inhibiting the production of compounds in the body which are involved in tissue inflammation and fever. Aspirin also ‘thins’ the blood by interfering with the ability of the blood to clot, and is used by health professionals in those at risk of heart attacks and strokes. There is also emerging evidence that aspirin may even reduce the risk of certain cancers.

Like all medicines, aspirin and NSAIDs have side effects. Common side effects include bruising and stomach upset (or even ulcers or bleeding from the bowel), at high dose. Very high doses may cause confusion or ringing in the ears (tinnitus). Aspirin should not be used in children, as it can trigger severe liver damage (known as Reye’s syndrome). Ibuprofen (Nurofen) and other NSAIDs are safe to use in children.

An aspirin allergy or sensitivity, or a reaction to NSAIDs, can cause symptoms that range from mild to severe. Reactions occur within minutes to hours of taking the medication. They may include:

• Hives
• Itchy skin
• Runny nose
• Red eyes
• Swelling of the lips, tongue or face
• Coughing, wheezing or shortness of breath
• Anaphylaxis — a rare, life-threatening allergic reaction

If you have asthma, nasal polyps, chronic sinusitis or chronic hives (urticaria), you’re more likely to have a reaction to aspirin or NSAIDs. When a reaction occurs, it can worsen symptoms of these conditions.

Read more about aspirin and salicylate intolerance

What if I suffer from another allergy?

Some drugs, such as penicillin and some anaesthetics, vaccines and other injections used in, for example, X-ray techniques, are known to be more likely to cause allergic reactions. They are used more cautiously for allergic people. If you suffer a fairly severe adverse reaction to a drug, or a repeated reaction on different occasions, this will usually be considered to be an allergy. It is important that this should be recorded in your medical notes and you should not be given the drug again. In each group of drugs, there are some that are less likely to cause allergic reactions.