Drug Allergy


A drug aller­gy occurs when the immune sys­tem over­re­acts to a sub­stance with­in the drug itself. A drug aller­gy can come from any form of med­ica­tion, whether it is in liq­uid, pill or injectable form.


All med­ica­tions can trig­ger an aller­gic reac­tion, but the most com­mon aller­gy induc­ing med­ica­tions are:

  • Antibi­otics, such as penicillin
  • Aspirin and non-steroidal anti-inflam­ma­to­ry med­ica­tions, such as ibuprofen
  • Anti­con­vul­sants
  • Mon­o­clon­al anti­body therapy
  • Chemother­a­py

The chances of devel­op­ing an aller­gy are high­er when you take the med­ica­tion fre­quent­ly or when it is rubbed on the skin or giv­en by injec­tion, rather than tak­en by mouth.


You may not devel­op an aller­gic reac­tion to a drug the first time it is admin­is­tered but devel­op an aller­gic reac­tion the next time you take the drug. In this case, your body has built anti­bod­ies against it and will devel­op symp­toms as the body tries to defend against the drug re-enter­ing your system. 

The most com­mon symp­toms asso­ci­at­ed with a drug aller­gy are:

  • Skin rash or hives
  • Itch­ing
  • Wheez­ing or oth­er breath­ing problems
  • Swelling
  • Vom­it­ing
  • Feel­ing dizzy or light-headed
  • Ana­phy­lax­is


Drug aller­gies can be hard to diag­nose, but you can meet with an aller­gist who will dive into your health his­to­ry look­ing for any con­sis­tent trig­gers to deter­mine if your symp­toms are aller­gic or non-aller­gic. Your aller­gist may also rec­om­mend a skin test or blood test to deter­mine if the drug of con­cern is affect­ing your sys­tem. In some cas­es, an aller­gist will rec­om­mend an oral drug chal­lenge to deter­mine the aller­gy, which is done under the direct super­vi­sion of an aller­gist in a doctor’s office.

Man­age­ment and Treat­ment

To man­age a drug allergy: 

  • Make sure all of your doc­tors are aware of your aller­gy and the symp­toms you experienced.
  • Ask about relat­ed drugs that you should avoid.
  • Ask about alter­na­tives to the drug that caused your aller­gic reaction.
  • Wear an emer­gency med­ical alert bracelet or neck­lace that iden­ti­fies your allergy.

If there is not a suit­able alter­na­tive to the drug you are aller­gic to, you may need to under­go drug desen­si­ti­za­tion.

If your drug aller­gy is life threat­en­ing, injectable epi­neph­rine is usu­al­ly pre­scribed as emer­gency med­ica­tion for treat­ing a life-threat­en­ing allergy.