Drug Allergy
Drug allergy is the body’s response to a drug. It is an unexpected, unpredictable immune system reaction that is not related to the effects of the drug itself.
When you take a drug, adverse reactions can occur depending on the dose and the possible interaction with other drugs.
However, there are other types of drug reactions that are unpredictable and have nothing to do with dose or possible drug interactions. This group includes reactions caused by allergies to drugs.
Types of allergic reactions to medications
Depending on where the reaction occurs, symptoms can range from hives and severe itching, a generalized rash and swelling, to bouts of bronchospam and even anaphylaxis.
Allergic drug reactions are divided into two groups, based on how quickly they appear:
- Immediate reactions : appear within the first hour of taking the medicine. It is triggered by the production of antibody or immunoglobulin E (IgE). This is the most commonly diagnosed type of reaction, and it is serious in nature.
- Delayed reactions : they appear after an hour of taking the medicine, although they can often take weeks to develop. This type of drug allergy is triggered by different immune mechanisms, and can lead to various types of reaction.
How often and at what age does a drug allergy appear?
Allergic drug reactions can appear at any age. However, they usually appear around the age of 40.
At this age, it is more normal to need to take more medications than younger people. Therefore, the possibility of sensitization increases with repeated taking of the drugs.
The frequency of this type of allergic reactions is difficult to specify, since there are no studies on its real incidence. However, it is estimated that they are around 10% of all adverse drug reactions.
About 5% of adults may be allergic to one or more medications. But it is estimated that 15-25% of the general population may have some kind of reaction with the medication they are using.
How can a drug allergy be diagnosed?
The most common allergic reactions are those caused by beta-lactam antibiotics and non-steroidal anti-inflammatory drugs (NSAIDs).
Diagnosis is based on a detailed medical history of the allergy-causing reaction and medications. To confirm this, laboratory tests and tests are done on the person, such as skin tests or controlled exposure tests.
Skin tests
They are the most common and can be intracutaneous, with immediate reading of the result at 15 minutes, or epicutaneous or patch reading at 48 and 96 hours.
The type of test is chosen based on the type and severity of the allergic reaction. The condition of the patient and the need for the drug in question are also taken into account.
Skin tests consist of introducing small amounts of the drug under study into the skin in different ways.
To carry them out, drug concentrations that have been shown to be non-irritating should be used. Otherwise, they could lead to false positives.
When performing the tests, the patient may experience the allergic reaction that he suffered when taking the drug. For this reason, the entire procedure must be well controlled and supervised by experienced personnel.
Controlled exposure tests
In certain cases, controlled drug exposure tests may be necessary , they are done when the rest of the previous tests have been negative and confirmation is necessary.
To carry them out, increasing amounts of the drug are administered orally and from time to time, until the therapeutic dose is reached.
A common reaction
Drug allergy cannot be prevented unless you have been diagnosed. In that case, your doctor will rule out the use of that drug and those of the same family.
However, remember the importance of taking medications only when necessary and following the instructions given by your doctor or pharmacist.
