Drug allergy: learn to recognize

Written by: Dra. Purificación González Delgado
Published: | Updated: 15/10/2018
Edited by: Top Doctors®

Some patients may have adverse side effects such as headache, nausea or dry mouth after taking drugs. However, in some rarer cases the patient may have an allergic reaction.


It is important to distinguish between a side effect to a drug and an allergic reaction, since side effects may occur in any person if you take enough doses and on the other hand, allergic reactions occur in a very small percentage of the population. In allergic reactions, also called hypersensitivity is involved the immune system, which identifies the drug as an aggressive substance and tries to eliminate it . In most cases the body sensitizes prior contact and in a subsequent contact with the drug when the allergy symptoms are triggered.


Symptoms of drug allergy


The most common symptoms of an allergic reaction in many cases usually appear immediately after the seizure, the most common:

  • Wheals on the skin, are pruritic and have a reddish color.  
  • Swelling of the facial region, throat and extremities.
  • Difficulty breathing, often with hoarseness or wheezing (breathing sounds)
  • Anaphylaxis: is the most severe case , usually appears a few minutes after taking a drug and usually accompanied by generalized itching with difficulty breathing and swallowing. Usually also have abdominal pain, vomiting, weakness, rapid pulse, dizziness and in severe cases loss of consciousness.

In rare cases, reactions occur days or weeks after starting treatment, they are called delayed reactions, the most common: 

  • Skin rash: rash similar to measles extending in much of the body, not usually very itchy and are not associated with other symptoms, often being mild.

More severe and infrequent processes include:

  • Serum sickness: fever accompanied by rash, edema, nausea ...
  • DRESS syndrome. Associated rash, increased eosinophilic leukocytes type (blood cells), generalized edema, increased lymph node size, liver involvement ...


Drugs that cause allergic reactions

Some of the drugs responsible for causing the most common allergic reactions are:

  • Antibiotics (especially penicillin and derivatives)
  • Aspirin and anti - inflammatory non - steroidal s.
  • Drugs used in chemotherapy


Drug allergy: When did see a doctor?


You should consult a specialist in Allergology if after taking a drug the following symptoms:

  • Difficulty breathing, wheezing.
  • Chest tightness
  • Edema, swelling of the facial region or the pharyngeal region
  • Feeling sick very intense


Drug allergy: diagnosis


After a careful history, sometimes other tests such as skin tests are very useful in the diagnosis of allergic reaction to penicillin or its derivatives (cefaloporinas amoxicillin) are requested, although for many other groups of drugs skin tests are useless.

Another option is to perform blood tests (specific IgE) are useful in case of allergy to penicillin and derivatives but with little use for other drugs.


Test drug exposure


If the drug is very important for the healing process and there are few alternatives to it or allergist determines that a drug allergy is highly unlikely, the patient receives small amounts that are increasing tolerance to confirm it.



Common causes of drug allergy


There are several causes that predispose the patient to submit to a drug allergy:

  • previous allergic reactions to other drugs
  • Patients with high exposure to a drug, either by receiving high doses, exposure to very frequent cycles, their prolonged use ...
  • previous HIV disease
  • family history of allergic reactions to drugs




Treatment of allergic reactions to drugs



Sometimes the drug suspension is sufficient but in other cases, if the patient presents bothersome symptoms, prescription antihistamines, corticosteroids required and in case of anaphylaxis, dealing with adrenaline and other life support measures.


Preventing drug allergy


There are some prevention tips to avoid problems arising from the allergic reaction to the drug:

  • Inform the doctor or nurse healthcare provider who will go to meet
  • Wear a medical alert as a bracelet, pendant or card in the name of the drug specified to which you are allergic
*Translated with Google translator. We apologize for any imperfection

By Dra. Purificación González Delgado
Allergy & Immunology

Dra. González Delgado is an expert renowned in Allergology of the city of Alicante. She graduated in Medicine and Surgery from the University of Valladolid, with a double major in Allergology via MIR and specific Pediatrics and the General Hospital of Alicante areas. He is also a Doctor of Medicine from the University of Granada. Currently she holds the Vithas Perpetual Help Hospital and Clinic. In addition, he is honorary professor of Medicine at the University Miguel Hernandez and national coordinator of clinical trial Immunotherapy. In addition, Dr. González Delgado has more than 20 articles in scientific and communications more than 50 national and international congresses magazines.


*Translated with Google translator. We apologize for any imperfection

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