Drug Allergy

Please see our free downloadable Factsheets at bottom of this page for more information about drug allergy and adverse reactions to medicines. You can also find information about aspirin intolerance and salicylates.

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.

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.

Side effects

All medications can cause side effects because of the way they work. The majority of people experience very few, or none, but some people are more prone to these side effects. The most common are:

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).

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:

Always ask whether the allergy has been recorded in your notes.
Volunteer the information to everyone who is involved in your care, even if they don’t ask.
Make sure you are given an allergy bracelet when you are in hospital.
If your allergy is severe, consider wearing your own allergy bracelet.
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.

Where would I go/who would I speak to if I wasn’t sure how to use my allergy medications?

A pharmacist is well placed to educate you on how to use your allergy medication and devices at the time of dispensing or on request. Your GP or nurse should also be able to do this. In the unlikely event that they are not able to help they will be able to advise you on where to find the information you need.

Aspirin intolerance and salicylates

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.