Medication Allergies

Allergy UK Drug Allergy reminds us that a drug allergy is the abnormal reaction of your immune system to a medication. Any medication be it over the counter, prescription, or herbal is capable of inducing a drug allergy. However, a drug allergy is more likely with certain medications for example:

• Penicillin and other antibiotics e.g., Phenoxymethylpenicillin and Amoxicillin. 
• Antiseizure medications e.g., Carbamazepine and Lamotriigine.
• Nonsteroidal anti-inflammatory drugs (NSAIDs), e.g., Aspirin, Naproxen, and Ibuprofen.
• Chemotherapy drugs e.g., Procarbazine and Paclitaxel.

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. 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 allergies are notoriously over diagnosed especially antibiotic allergies. According to  Dr Helen Allergy UK Around 10% of the UK population report a penicillin allergy, and yet only 1% are likely to be truly allergic. It is vital to diagnose drug allergies correctly and failure to do so can result in increasingly complex drugs being used which are unnecessary and have the potential to cause more harm. Many drugs cause side effects such as diarrhoea, abdominal pain, dry mouth etc but it is important to differentiate these from true allergic reactions.

True drug allergy signs and symptoms may include one or a combination of symptoms including:

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

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).