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Drug allergy

A drug allergy is a hypersensitivity to a certain substance of a drug, most commonly a medication. This hypersensitivity is causing about 10% of drug side effects. Side effects may vary, from mild, as rashes on a well-defined skin area, to very severe life-threatening reactions. The allergic immune response may affect different organs, but skin symptoms are the most common. It is essential to recognize symptoms in due time, because they may lead to life-threatening conditions.

An allergic reaction will not occur on the first intake of the medication, but on the second or later occasion.

Disagreeable side effects are far from being all allergic; about 10% of drug side effects are of allergic origin.

The hypersensitivity is triggered by a drug component what the immune system considers as invader, antigen. Typically the first exposure allows the body to create antibodies for the antigen. On the second and later exposures the antibodies of the drug antigen provoke the secretion of inflammatory mediators. Most important of them is the histamine. Impacts of mediators on cells, tissues, organs are liable for the symptoms. 

The following is a short list of the most common drug allergens:
  • analgesics, anti-inflammatory drugs e.g. codeine, morphine; non- steroidal anti-inflammatory medicines, e.g. ibuprofen, salicylate
  • antibiotics, e.g.: penicillin, sulpha drugs, tetracycline
  • antiepileptics (antiseizure spasmodics) e.g. phenytoin, carbamazepine
  • Generally, medications working as a hapten, tend to trigger allergies when attaching to a carrier protein, or they are big enough (i.e. insulin molecule) to activate the immune system

There is a higher risk of allergic reactions in the following cases:
  • frequent, long lasting and/or high dose drug administration 
  • administering by injection, not by ingestion
  • patient or patient’s family members are prone to allergy 
  • patient or patient’s family members have asthma
  • patient is allergic to different foods, such as egg, soy.