Allergy To Drugs

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Allergy To Drugs
Allergy To Drugs

Video: Allergy To Drugs

Video: Allergy To Drugs
Video: Drug Allergy | Dr. Madhavi Kadambi 2023, September

Drug allergy

Medicines are an indispensable part of the treatment of diseases. In principle, however, any drug can also have undesirable effects. These include side effects, intolerances and allergies.


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  • Advice, downloads & tools
  • Adverse drug effects
  • When do we speak of a drug allergy?
  • What are the symptoms of a drug allergy?
  • ">How is the diagnosis made?


  • How is drug allergy treated?
  • Whom can I ask?


Adverse drug effects

According to the WHO (World Health Organization), adverse drug reactions (ADRs) are defined as reactions to drugs (administered in the usual dose) that are unintentional and harmful.

A distinction is made between adverse drug reactions:

  • Type A reactions: are common and predictable. They can happen to everyone. 80 percent of adverse drug reactions are type A reactions. Examples of this are side effects, as can be seen in the accompanying text of medication, such as diarrhea and fungal infections after antibiotics or hair loss after chemotherapy.
  • Type B reactions: are unpredictable and require an individual tendency. Type B reactions are also known as drug intolerance or drug hypersensitivity reactions (hypersensitivity). Drug allergies also belong to this group; typical examples are asthma attacks and lip swelling on pain medication or skin rashes on antibiotics.

When do we speak of a drug allergy?

In the case of a drug allergy, there is an excessive reaction of the immune system to drugs or their breakdown products (metabolites). In extremely rare cases, this reaction can also be triggered by the dyes or preservatives contained in a drug. In order for this to happen at all, there must be an allergic reaction. Drug allergies often occur, for example, with anti-epileptic drugs, antibiotics or narcotic substances.

On the other hand, drug intolerance does not result in an overreaction of the immune system, but body cells are activated directly, which shows certain reactions.

As a rule of thumb, it can be assumed that drug allergies usually start within the first six weeks after starting a new drug, and allergies are unlikely with longer use.

Note It is important that all substances ingested, including natural remedies, food supplements, etc., can trigger such reactions.

What are the symptoms of a drug allergy?

A drug allergy manifests itself in different ways. The allergic symptoms are most common on the skin - but mucous membranes and internal organs can also be affected. The time of the first signs of allergy varies. In the case of immediate-type allergies, they occur immediately; in case of late-type allergies, they occur only after 24 to 72 hours. It is important to thoroughly clarify possible drug allergies. On the one hand, because repeated administration can lead to severe symptoms, on the other hand, also in order not to restrict future therapy options by unnecessarily withholding potentially important and well-tolerated medication.

In the treatment of drug allergy, the absolute avoidance of the responsible drug is in the foreground. An allergy pass is also issued. There are several drugs available to treat acute symptoms - especially cortisone and antihistamines. In-patient or emergency treatment may be necessary in the case of severe allergies.

From rashes to anaphylactic shock

In the context of the immediate type reaction mentioned above, a very itchy, nodular or patchy rash can occur, which can also affect the mucous membrane. Symptoms also include urticaria (hives) and what is known as angioedema. This is a swelling of the skin or mucous membrane, which can be life-threatening - especially if the pharynx swells. Rashes that spread to the mucous membranes (e.g. the mouth area) require rapid medical attention. If you experience breathing difficulties, you should seek immediate medical attention as this could be a sign of a severe asthma attack or anaphylactic shock.

Anaphylactic shock (anaphylaxis) is a particularly strong and life-threatening allergic reaction. In this case, acute, massive allergic reactions of the immediate type occur which affect the whole body. It comes, among other things, to narrowing of the airways, to cramps, to vomiting up to cardiovascular and respiratory arrest with organ failure. Anaphylaxis is always a medical emergency and requires immediate medical attention. For more information, see Emergency - Allergic Reaction.

Other symptoms of drug allergy include vasculitis (inflammation of the blood vessels) or blood disorders.

The most common form of drug allergy is the late-type allergy to the skin, in which itchy eczema, typically hundreds to thousands of a few millimeters in size, forms, which heal after days to weeks with flaking. If a drug is used in cream form,

Stevenson-Johnson Syndrome, TEN, and DRESS: rare but dangerous

Late-type allergies can rarely trigger very severe drug allergies. In Stevenson-Johnson syndrome, blisters and reddening of the skin appear. This loosens flat. The syndrome requires immediate medical treatment. Infections and dangerous water loss can occur. Most often, drugs from the group of sulfonamides and pyrazolones trigger Stevenson-Johnson syndrome. If more than 30 percent of the body surface is affected, one speaks of toxic epidermal necrolysis (TEN), in which the risk of mortality increases considerably. These reactions can also be triggered less often by infections - usually with herpes viruses. There are also other similar drug reactions such as DRESS syndrome.

How is the diagnosis made?

Since the diagnosis of drug allergies is very complex and not entirely harmless and the resources for diagnostics are limited, only (life) important drugs such as painkillers, antibiotics, local anesthetics and anesthetics are generally subjected to extensive testing. However, each individual case must be assessed individually.

In the diagnosis of drug allergies, skin and blood tests as well as so-called provocation tests are used. In order to achieve the most reliable test results possible, the diagnostic work-up should take place no earlier than six weeks - but no later than six months - after the symptoms have subsided. The medical history is recorded in detail (e.g. whether allergies are already present, how reactions have shown after taking a drug, etc.). Reliable blood and skin tests to clarify allergies are only available for a few drugs (e.g. penicillin). Often the so-called provocation test must be used in order to diagnose or rule out a drug allergy. But even this one cannot give complete certainty.

Skin tests

The following skin tests are used:

  • Prick test: In this test, the forearm is marked and a drug is applied in liquid or in liquid drop form. A lancet (a small piercing instrument) is then used to pierce one millimeter deep into the skin below the drop of solution. Skin reactions can be observed after twenty minutes at the latest.
  • Scratch test: The skin on the inside of the forearm is scratched about one centimeter long (without bleeding). Then allergens are applied in liquid form, which can trigger reactions on the skin.
  • Intracutaneous test: An allergen solution is injected into the skin to make skin reactions visible.
  • Patch test: The drug is placed under a plaster in liquid form or crushed for 24 to 48 hours. Immediate reactions are visible after 20 minutes, delayed reactions after six to eight hours. Late reactions are visible after 24 or 48 hours (in the case of patch tests also after 72 hours).

Intracutaneous and skin prick tests are suitable, for example, for detecting allergies of the immediate type and, by reading after one or two days, also of the delayed type. Only in a few cases can skin tests alone determine the allergy-causing drug.

Blood tests

Blood tests are also used in the diagnosis of drug allergies, e.g. the detection of specific IgE (allergy-characteristic antibodies). Particularly reliable routine investigations are only available for reactions to so-called ß-lactam antibiotics. A blood test alone is rarely sufficient to confirm the allergy. In addition to specific blood tests, it is advisable to determine the differential blood count, liver and kidney values and inflammation parameters (e.g. C-reactive protein).

Provocation test

In a provocation test, the patient is given the drug in increasing doses in open form or, in the case of placebo (drug without active ingredient), in a controlled form, alternating with a placebo drug for swallowing or in the vein. In exceptional cases, tests via nasal (via the nose) or bronchial (via the bronchi) provocation are also possible. This test usually only takes place under inpatient conditions (in a hospital), as it is associated with certain risks. Therefore, this form of testing is only carried out if there is no other alternative and there was a very severe reaction with a suspicious drug in the medical history. However, the provocation test does not allowReliable differentiation between a real allergy and an intolerance - only the substance to which the reaction occurs can be confirmed with a high degree of probability and subsequently avoided. Even if the result is negative, that does not mean that there cannot be a new awareness at a later point in time.

How is drug allergy treated?

The drug responsible for the drug allergy must be avoided in any case and is entered in the allergy passport. This should always be carried with you in emergencies! However, if the drug allergy has been ruled out by the test, the consequences should also be drawn and any existing, old and thus no longer valid allergy passports should be destroyed.

If a drug allergy occurs, there are several drug treatment options available - especially cortisone and antihistamines. In severe cases, hospitalization or emergency treatment may be necessary. For more information, see Emergency Allergic Response.

Whom can I ask?

The diagnosis and therapy of a drug allergy are carried out by the following bodies:

  • Specialist in dermatology and venereology,
  • Allergy outpatient clinic,
  • Allergy outpatient clinic in a hospital with a dermatological ward.

For an outpatient clinic, you need a referral from your attending doctor.