Drug Allergies Branch

Unwanted and harmful effects that occur during the use of all kinds of drugs, if our immune system perceives these drugs as a foreign substance and reacts then called drug allergy. Only part of the drug reactions are allergic reactions. Drug allergies may present with very different findings. Diagnosis and treatment require experience and should be done at Drug Allergies Branch.

What is Drug Allergy?

Drug allergy is defined as the immune system’s perception of a drug as a foreign substance and showing reaction. Various symptoms occur during the use of drugs for different purposes. Most of them do not result from the reaction of our immune system and are not allergic. But all these symptoms are mistakenly called drug allergy. Occurring symptoms must be evaluated by allergy specialists (at a drug allergies branch) to determine whether the symptoms are allergic or not or (if it is allergic) what kind of allergic reaction it is. Because some reactions can be severe and can be life-threatening.

What is the Frequency of Drug Allergy?

Admission to hospital for adverse reactions to drugs in children constitutes 0.4-10.3% of all hospital admissions. 0,6-16,8% drug reactions develop in hospitalized children. 40-50% of these are allergic reactions. In a study conducted in our country, drug allergy was reported in 2.8% of children aged 6-9 years.

What Are the Symptoms of Drug Allergy?

Drug allergies may present with various symptoms. Some of these may be life-threatening severe reactions. According to the type of allergic reaction, the symptoms may be as short as 0.5-1 hours after taking the drug, and some may be seen days later.

The most common findings may be skin rash, itching hives (urticaria), skin rashes, shortness of breath, runny nose, sneezing. Although it is rare, the most serious finding is anaphylaxis called allergic shock. In anaphylaxis, there will be hives, drop in blood pressure, diarrhea, vomiting, shortness of breath and fainting within 0.5-1 hours after taking the drug. If proper intervention is not made on time, it can be life-threatening.

In some cases, symptoms appear after a few weeks of medication intake and this makes diagnosis more difficult. The most important of these late reactions are Stevens Johnson Syndrome / Toxic Epidermal Necrolysis, which is characterized by drug fever, drug-related anemia, liver and kidney pathologies, serum disease and extensive skin and internal organ involvement.

Which drugs are the most common causes of drug allergy?

Any drug can cause allergies. But some of them cause more often. The most common antibiotic group in children is penicillin called beta lactam. Secondly, aspirin and non-steroid pain relievers and antipyretics, followed by preoperative muscle relaxants, radiocontrast agents used for examinations and drugs used for cancer treatment.

What are the risk factors for drug allergy?

Some factors increase the risk of drug allergy. These factors are divided into drugs or the person himself.

Drug factors;

  • Frequent consumption of the drug
  • Structural properties of the drug
  • The route of administration: Intravenous administration poses more risk than oral intake
  • Frequency of application: Frequent and prolonged use increases the risk.

Individual factors

  • Age: Children are less common than adults.
  • Hereditary predisposition: Some hereditary structures increase the risk of allergies to certain drugs.
  • Having liver and kidney disease in children
  • Having allergy to same medication or another drug before
  • A disease that weakens the immune system or requires frequent medication (AIDS, Cystic fibrosis)
  • Drug allergy in the family

When to see a doctor for drug allergy?

In case of any drug allergy suspicion, it will be very helpful to contact an allergy specialist trained and experienced on this subject as soon as possible at a drug allergies branch. Drug allergies occur with very different symptoms and some of them are very dangerous reactions. Therefore, the patient should be evaluated as soon as possible and correctly diagnosed and treated.

How to Prepare for Examination on a Drug Allergy?

It is useful to make some preparations when you go to the doctor for drug allergy to make the examination more efficient.

  • Note any signs and symptoms that occur after drug use. Photograph any external skin symptoms and show them to your doctor.
  • Bring along the medications you take or make a note of their names.
  • If you have any previous examinations and x-rays, bring them with you.
  • Take notes before you come to remember what you want to know about drug allergies and your child’s condition.
  • If allergy tests are required for diagnosis, discontinue allergy syrup and pills, cough syrup and cold medications 1 week before arrival for not to avoid testing.

How to Diagnose Drug Allergy?

  • In order to diagnose the patient correctly, it will be appropriate for the allergy specialist to evaluate and perform the necessary tests.
  • A good history should be obtained for correct diagnosis. The relationship between the reaction and the drug should be evaluated. The type of reaction should be decided. Personal risks should be assessed.
  • Afterwards, a detailed examination should be performed to detect any symptoms. But if the time has passed, the child may have completely returned to normal and had no symptoms.
  • First, complete blood count, C-reactive protein, sedimentation, if there is symptom lung film and liver and kidney functions can be ordered.

Blood allergy tests for drug allergy diagnosis

Blood tests may be performed to diagnose drug allergy. However, it is possible to diagnose very few drugs blood tests. In addition, the negative result is not very reliable. It does not prove you have no allergies. In recent years, a test called basophil activation test has been used in drug allergies. Drug allergy tests with Basophil activation are performed at İstanbul Allergy. The interpretation of this test also requires experience. The results of this test tells us if there will be serious reactions or not with 80% probability. With this method, it is safe to determine whether there are allergies to many drugs at the same time.

Skin allergy test in the diagnosis of drug allergy

Allergy tests on the skin comes first to find the suspected drugs for drug allergies. In this test, drugs that may be responsible for allergy are dripped into the arm, with tip of a sharp object it is pushed onto the skin and sent into the skin and early and late reading is done according to the type of reaction. If a certain amount of redness occurs at the dropping place, that drug is considered allergic. If this test is negative, the drugs are injected into the skin by diluting to a certain concentration and it is evaluated whether or not allergies develop. If the allergy does not occur in this test too, it is checked whether the drug develops allergy by taking orally or injecting. As a result of these tests, it is decided whether there is an allergy or not.

However, it is very important to be performed by pediatric allergy specialists who are experienced in this field in order to avoid any inaccuracies in performing and evaluating skin allergy tests.

Provocation tests in the diagnosis of drug allergy

If there is a suspicion of drug allergy and the skin tests are negative, the doctor will assess whether the drug is reacting with giving increasing doses. However, due to the possibility of a severe reaction to the drug, it must be carried out by an allergy specialist under observation and at a drug allergies branch with intervention conditions.


The first aim of the treatment is to treat the findings when the patient is seen. The first thing to do is discontinue the medication used. Drug treatments are then performed according to the seriousness of the reaction. In mild reactions, syrup or pills containing antihistamine are used. Cortisone-containing drugs can be used for short periods of 3-5 days in cases where it is more severe and does not improve with antihistamines. 

If anaphylaxis (allergic shock) develops, adrenaline should be administered immediately and hospitalized and other treatments should be applied.


If the patient is allergic to a drug and must use that drug, desensitization process should be done. In this process, the drug is started with very small doses and given at 15-30 minute intervals, and the patient becomes insensitive to that drug. However, this is only valid during that treatment. When it is necessary to take a break and use it again, it becomes allergic again and the same process must be repeated.

What should be done for protection to drug allergies?

Medications that should not be used by the family should be given as listed. The patient should state that he/she has a drug allergy when he goes to any health institution. It should also bear a name card or tag, indicating which drug you are allergic to. It will be very useful for health teams to know that the patient is allergic to a drug in case of an emergency intervention.

Adrenaline auto injectors should be given to the family and taught to be used in cases where anaphylaxis (allergic shock) develops depending on the drug.


  • Drug-specific IgE tests
  • Basophil activation tests for drugs
  • Drug allergy tests, skin prick and intradermal tests
  • Drug provocation tests
  • Penicillin and other antibiotic allergy tests
  • Local anesthetic and general anesthetic allergy tests

What should I be aware of when I come to have a Drug Allergy Test?

Some drugs that may affect the results of allergy tests need to be discontinued 1 week before the allergy test. Some of these drugs are; cough syrups, cold medicines, allergy medications. Antibiotics and inhaled drugs do not affect allergy tests. During an allergy test, the child should not have breathlessness.

At what age can drug allergy tests be done?

Drug allergy tests made from blood can be done at any age. Skin allergy tests are usually done in people older than 5-6 years, as they are painful and difficult to assess.