Drug allergy

The British Society for Allergy and Clinical Immunology (BSACI) defines drug allergy as an adverse drug reaction with an established immunological mechanism.

Hospital Episode Statistics from 1996 to 2000 reported that drug allergies and adverse drug reactions accounted for approximately 62,000 hospital admissions in England each year

• evidence that these reactions are increasing:
  • between 1998 and 2005, serious adverse drug reactions rose 2.6-fold
  • up to 15% of inpatients have their hospital stay prolonged as a result of an adverse drug reaction

About half a million people admitted to NHS hospitals each year have a diagnostic 'label' of drug allergy, with the most common being penicillin allergy.

• about 10% of the general population claim to have a penicillin allergy; this has often been because of a skin rash that occurred during a course of penicillin in childhood. Fewer than 10% of people who think they are allergic to penicillin are truly allergic (1). Therefore, penicillin allergy can potentially be excluded in 9% of the population.

Allergic reactions to non-steroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen, diclofenac, naproxen and aspirin, are common

• in particular, 5-10% of people with asthma are affected.
  • about one-third of people with chronic urticaria have severe reactions to NSAIDs, involving angioedema and anaphylaxis.

Anaphylaxis-type reactions occur in approximately 1 in 1000 of the general population. Anaphylaxis during general anaesthesia occurs in 1 in 10,000-20,000 anaesthetics

Reference:

• NICE (September 2014). Drug allergy: diagnosis and management of drug allergy in adults, children and young people