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Drug allergy, how to identify the source of the problem

In addition to environmental allergens such as pollens, house dust mites, fungi and animal epithelium, food, as well as medicines, can also cause us to be allergic. The experts of the “Health and prevention” blog elaborate on this reaction to some drugs.

Before taking some medicines, our body reacts by generating an unexpected, unpredictable immunological response, independent of the dose we have taken and of the interaction with other medicines we are taking at the same time an allergy.

The main drugs causing allergic reactions are beta-lactam antibiotics (penicillins and derivatives), non-steroidal anti-inflammatory drugs, iodinated contrast agents and muscle relaxants, according to the doctor Lourdes Romualdo, head of the Allergology Service at the Quirónsalud Marbella Hospitalcenter that precisely has a specific unit for the study of drug allergy.

These reactions, he points out, can be immediate (within the first hour of taking the medicine) or later (they appear hours or even weeks after taking the medicine), although the type of reaction that is diagnosed with more frequent is the immediate one, intervened by the presence of IgE.

It usually affects the skin in the form of hives, hives or hives, and sometimes parts of the body can swell.

Other times these reactions are more serious, being able to impact the respiratory tract, with coughing or a feeling of difficulty breathing and, in the most severe cases, with involvement of the cardiovascular system, appearing dizzy, hypotension and even loss of consciousness, which that requires immediate medical attention.

This severe and immediate allergic reaction after taking a medicine is what is called ‘anaphylactic shock’adds the allergist.

Whenever there is a suspicion of allergy to a medicine, especially if it belongs to one of the indicated pharmacological groups, it is important to do the allergy study in the specialized services for this, since the result of this study will confirm or rule out which group of medicines the patient is or is not allergic to, in order to limit as much as possible the medicines to avoid, he explains.

How to identify the source of the problem? The drug allergy study includes the patient’s detailed medical history as well as skin tests that are done on the forearm.

If these are positive, the patient would be diagnosed; if they are negative, controlled exposure tests with drugs are used in the hospital, in an observation room and under medical supervision in case a reaction similar to the one the patient previously had occurs.

Allergy to medicines, increasingly common

From the Spanish Society of Allergology and Clinical Immunology (SEAIC) maintain that allergic reactions to medicines represent the third reason for consultation (15% of consultations) in Allergology services.

They point out that these reactions are increasing according to the latest studies, an upward trend that could be justified by the fact that the population takes more drugs, but also because allergic reactions have increased in general.

“Allergy to medicines is the first cause of consultations for admitted patients and the second after rhinitis and allergic asthma in appointments for external consultations”, postulates the allergist from Quirónsalud Marbella.

The case of antibiotics

Dr. Romualdo points out that antibiotics are one of the most used medicines in the hospital and also in Primary Care; for this reason it is important to consider the history of allergy to antimicrobials before prescribing and proceeding with their administration.

In fact, it highlights the high prevalence of allergy to beta-lactams, which are widely used in daily clinical practice due to their broad antimicrobial spectrum, and which are currently the most frequent cause of adverse drug reactions together with non-steroidal anti-inflammatory drugs.

allergy medications
PHOTO EFE/André Coelho

On the other hand, the accuracy of the diagnosis is very important due to the detection of a high percentage of patients who mistakenly believe they are affected by penicillin allergy.

“Of the people who believe they are allergic to penicillin, only about 30% are, and this leads to the use of drugs that are less effective, more toxic and more expensive than first-line treatments. In patients admitted to hospital, the label of penicillin allergy takes on greater significance, as it conditions the use of alternative drugs”, laments the doctor.

He thus underlines that the consequences in this case are “clear”, since this may mean an alternative treatment of second choice and that insufficiently covers the microorganisms to which the patient is exposed in this infection, potentially increasing morbidity and mortality, a longer duration of the hospital stay, as well as an increase in hospital costs.

For this reason, the head of the Allergology Service at Quirónsalud Marbella Hospital insists that the diagnosis of penicillin allergy must be as accurate as possible, in order to “remove the false label of penicillin allergy that 70% of the remaining patients have”.

What about anti-inflammatories?

In his opinion, another relevant piece of data is the impact of non-steroidal anti-inflammatory drugs: “This group is the second most frequent cause of drug allergy consultation, and its study is of great relevance due to its involvement in processes of analgesia, as well as in the symptomatic treatment of various inflammatory diseases”.

Finally, he emphasizes that the study of allergic reactions to both iodinated contrast agents and muscle relaxants used in surgical interventions deserve special attention due to the importance of these drugs for both diagnostic and therapeutic purposes.

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