Causes of AllergyDrug Allergy
Drug Allergy
Image: Renjith Krishnan/FreeDigitalPhotos.net		 According to the World Health Organization the adverse reaction to drugs are a unwanted harmful effects after taking a drug to the normal dose used to prevent, diagnose and/or treat a disease.

5 to 100% of all drug side effects are allergic: the body defense system reacts far too much of expected.

The commonest drugs inducing allergy in Spain are antibiotics (mainly penicillin) and non-steroideal anti-immflamatory drugs (NSAIDs).

Allergic reaction to drugs are produced by an immune system attack to the drug molecule.

Drugs are clearly beneficial to people and help fighting diseases. Some adverse reaction of non-allergic origen are:
Drug Intolerance: some patients may notice that erythromycin may cause stomach pain or diarrhea.
Less capacity to break up the drug than normal; may be due to a liver or kid problem.
Two or more drugs in the body at the same time competing to be broke up through the same mechanism. This may cause a higher blood level of the drug. The antibiotic erythromycin and the bronchodilator theophyline given at the same time may cause side effects.
Lack of an enzyme responsible of breaking up the drug.
A drug overdose: it may be toxic and trigger symptoms, especially if given for long periods. The antibiotic vancomycin may cause ear and kidney problems when used for a long period.

The most severe reaction to a drug is called Anaphylaxis




More information

How to act when you are allergic to certain drugs

3 to 6% of hospital admissions are due to drug reactions

Drug Allergy: Spanish Society Allergy paper (spanish).