Drug allergy symptoms

Between 5-10% of people in the UK have a drug allergy, with these being the most common symptoms:

  • rash  
  • itchy face and eyes
  • hives 
  • wheeze
  • facial swelling 
  • anaphylaxis

This allergy could be to a drug your GP has prescribed for you or a drug you've been given in hospital, such as:

  • penicillin and other antibiotics  
  • aspirin and other non-steroidal anti-inflammatory drugs, such as ibuprofen
  • anaesthetic drugs
  • anti-convulsant drugs
  • chemotherapy drugs

There are other substances that you could be allergic to such as the contrast dye used in X-rays or CT scanning. You could also have an allergy to the skin cleaning agents used in hospital and latex.

Confirming an allergic reaction

It is important to make sure that the reaction you have is actually an allergic reaction and not a side-effect of the medication, like feeling sick. We would ask you what symptoms you have and when they happen to help us know, but we may have to do more tests.

We may use skin testing as a way to check for allergic sensitisation to some drugs. If skin testing is not possible, or the result is unclear, we may get you to take the medication again, but under controlled conditions.

We do about six to ten drug challenges every month. This is to confirm if a drug was the cause of a reaction, but more often to identify safe alternatives.

Skin prick testing

Skin prick testing is a universal allergy test and often used to find out what is causing an allergy. 

Oral food challenge

Oral food challenges are tests that use suspected food allergens. The foods that we most commonly test are peanuts, tree nuts and shellfish.

Drug challenge testing

This form of testing comprises of a series of tests to see if you are allergic to certain drugs, all under close medical supervision. 

Molecular diagnosis

Molecular diagnosis covers tests which can assess whether someone has antibodies against a particular protein in a food which causes an allergic reaction.

Nose clinic tests

Patients coming to the nose clinic will have a number of tests, often including an examination using an endoscope, skin prick testing, chest peak expiratory flow and spirometry.

Nasal sprays

Corticosteroid nasal sprays or drops are the most effective standard treatment for hay fever and other nasal allergies.


Antihistamines prevent histamine causing the itching and swelling that occurs when you have allergies.


Allergen immunotherapy is a treatment in which the allergen that triggers an allergic reaction is given in order to suppress unnecessary reactions.

Allergy team contact details


Fulham wing/South block, Fulham Road

Tel:  +44 (0)20 7351 8892
Fax: +44 (0)20 7351 8949