Drug Allergy – Causes, Symptoms & Treatment

Drug allergy

If drugs or medicines lead to undesirable side effects, this can be due to a drug allergy , drug allergy or drug eruption . The body reacts very sensitively to certain drug ingredients, which is shown by an allergic skin rash .

What is a drug allergy?

In principle, any drug can trigger a drug allergy. Some medicines are much more likely to cause allergic reactions. For example, allergies occur in ten percent of all penicillin treatments , while allergies to the heart drug digoxin are very rare.

The term drug allergy or drug allergy describes, by definition, the increased reaction of the immune system to the ingredients of drugs. The inflammatory skin rash, also known as drug exanthema, starts from the connective tissue of the vessels and usually goes away again. The drug eruption can occur on individual parts of the body as well as distributed over the entire body.

In addition to the skin reaction, any other form of allergic reaction is also possible with a drug allergy, since drugs contain additives such as flavorings and colorings, stabilizers or fillers in addition to the ingredient or active ingredient. For this reason, a drug allergy can also be due to the excipients it contains.


The cause of the drug allergy is a dysregulation and an excessive immune system response to certain drug ingredients or excipients.

Active ingredients in, for example, psychotropic drugs , painkillers , antibiotics or thyroid drugs are often the cause of a drug allergy when used internally.

But even with a local application, for example through a local anesthetic, can be the cause of a drug allergy.

Preservatives in a drug, such as thiomersal or benzalkonium chloride, can also be a cause.

Symptoms, Ailments & Signs

In principle, a drug allergy can occur with any drug, but this is more common if the drug is taken for a longer period of time. Various symptoms can occur. In more severe cases, the body can react very violently a short time after ingestion, with shortness of breath and cardiovascular problems through to anaphylactic shock , which is life-threatening for those affected.

The most common form of a drug allergy is a reddish skin rash with small pustules or eczema (drug rash), which can be very itchy, and very itchy wheals can also form on the skin (hives). In some people, the mucous membranes can swell and they react with sneezing and a runny nose.

Swelling and rashes around the mouth can also occur . With eye drops, the eyes can react with reddening and increased tear flow. Gastrointestinal problems and nausea are also possible, as are headaches and a general feeling of illness.

If you have symptoms, you should always consult a doctor, because it is possible that a drug will be tolerated without any problems for a long time, but at some point the body will react with an allergy. The package insert contains information about possible allergies.


Drug allergy symptoms can vary in severity. As a result of drug therapy, allergic symptoms may occur in the form of hives , inflammatory skin rashes, water- or blood-filled blisters, patchy skin rashes, or contact dermatitis.

The symptoms can be accompanied by fever and poor general health. Various medications, such as antihistamines or glucocorticoids, can be used to treat drug allergies in order to alleviate the symptoms. As a rule, the allergic reactions to a drug are quite weak.

However, the symptoms can increase with repeated contact. Then, in addition to the skin reactions, additional symptoms such as dizziness , sweating , drowsiness, nettle rash, nausea , shortness of breath , swelling of the mucous membranes can manifest themselves. In this case, a circulatory collapse cannot be ruled out.


In the case of a drug allergy, only very limited treatment is possible. Since the patient has an intolerance to a certain substance, this intolerance cannot be eliminated directly in most cases. Many people develop drug allergies by taking a certain drug too often or for too long.

Here the body can react with allergic reactions to the ingredient. In most cases, however, a drug allergy can be avoided. In this case, the patient is switched to a different medication. This drug should of course have the same effect, but have a different ingredient so that the drug allergy is not triggered again or even increased.

If you continue to take the same drug, the drug allergy will not go away on its own and in most cases will get worse. The consequences of a drug allergy are usually a rash, headache or nausea. Symptoms vary widely and are individual to each patient and drug. In any case, if you have a drug allergy, you should consult a doctor or pharmacist, as these people can help you switch to another drug.

When should you go to the doctor?

If you have a drug allergy, you don’t necessarily have to go to the doctor. However, physical complaints that are clearly related to the medication should be discussed with a doctor. Switching to another drug is usually sufficient to prevent further allergic reactions. Medical advice is required at the latest when the allergic reactions affect the general condition and, for example, cause severe physical or psychological reactions.

Anyone who is unsure should consult a doctor – this is advisable at the latest in the event of panic attacks or anxiety. If severe symptoms such as swelling, edema or fever occur, a visit to the hospital is recommended. In order to enable rapid treatment, the responsible medication should always be carried along.

In the event of severe symptoms, an ambulance must be called. If, for example, there are circulatory problems or a high fever, it may be a severe allergic reaction that must be treated medically in any case. First aid measures may have to be carried out before the emergency services arrive.

Treatment & Therapy

As a rule, in order to diagnose a drug allergy , the drug that is presumably responsible is discontinued. If the symptoms improve after stopping, this is considered an indication of a drug allergy. However, the diagnosis is made more difficult when the affected person has to take several medications.

Here it is rarely possible to find the origin of the drug allergy. If skin rashes occur while taking medication, a doctor should always be consulted for clarification. A classic allergy test is only suitable to a limited extent for diagnosis, as this test can only detect an allergy to anti-inflammatory drugs or antibiotics.

Diagnosis can also be difficult when the drug allergy mimics other diseases. It is therefore difficult to correctly classify the reactions triggered by the allergy. In this case, it can also happen that an allergy remains undetected as the cause.

If the medication is discontinued after consultation with the doctor, the drug allergy usually takes a favorable course. The rash usually heals within a few days. The prognosis is somewhat less favorable if the body’s allergic reaction is very strong. Final healing can take up to six weeks.

Outlook & Forecast

Drug allergies usually have a good prognosis because they are usually triggered by certain active ingredients in a drug, e.g. B. can cause a skin rash (drug eruption) .

A rash associated with taking a drug can be a first sign of an allergic reaction. It usually disappears again quickly when the allergy-causing drug is discontinued or a switch to a different combination of active ingredients takes place.

It becomes somewhat more difficult if the allergic reaction is more severe and the general condition worsens as a result, perhaps in combination with fever, edema or swelling. Then an examination in the hospital makes sense. High fever and circulatory problems as a reaction to a drug are always a case for the emergency doctor .

The prospects are also somewhat less favorable if different drugs are taken, making the diagnosis more difficult. Sometimes the symptoms of a drug allergy resemble those of other diseases, making it difficult to pinpoint the exact cause.

Mild allergic reactions, such as a skin rash, usually get better within a few days of stopping the drug that caused the allergy, while severe allergic reactions may take several weeks to subside. In order to improve the prognosis, patients should inform their doctor early on about intolerance reactions.


Drug allergies cannot be prevented because the body can develop an allergy to any substance or ingredient. If allergic reactions to medicines have occurred in the past, it is advisable to inform the doctor.

In the case of self-medication of non-prescription drugs, the pharmacist should also be informed. It is also important that an allergy pass is carried with you in the event of a drug allergy. This should list the incompatible drugs and can even be life-saving in emergency situations.


A drug allergy cannot be cured. In order to avoid symptoms, the patient must discontinue the drug in question and no longer take it in the future. This will prevent the disease from recurring. This requires a high degree of personal responsibility in everyday life.

Follow-up care is basically aimed at tackling complications in a preventative manner. This happens in the context of a drug allergy through the knowledge transfer described above. This is particularly important in life-threatening situations. With treatment occurring within minutes, such knowledge can be vital. An allergy intolerance pass also helps if the patient is no longer responsive.

It literally saves lives. People with allergies can usually carry it around in their wallets. A comparison with another disease again shows the fundamental difference. After cancer has been diagnosed, regular follow-up examinations take place to prevent it from recurring. Since a drug allergy is always present, this method is not effective in this case. Protection against dangerous consequences can only be achieved by avoiding any substances.

You can do that yourself

Drug allergies cannot be prevented in every case or only to a limited extent. In principle, the body can develop an allergy to any ingredient or substance in a drug. However, this intolerance often only occurs when certain medicines have been consumed for too long or with too high an intensity.

In order to avoid such allergies, medication should only be consumed by the person concerned if this is absolutely necessary. This is especially true for the excessive consumption of painkillers . However, if an allergic reaction to a product occurs, switching to a drug with different ingredients can help.

If the patient is already aware of previous allergic reactions, the treating doctor should be informed about them. The pharmacist should also be informed in the event of self-medication with non-prescription substances .

It is also important that those affected carry an allergy pass with them. The intolerable medicines or substances should be listed on these. In an emergency, carrying such a passport with you can help the doctor treating you to take appropriate countermeasures more quickly and thus save your life.

Lisa Newlon
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Hello! I am Lisa Newlon, and I am a medical writer and researcher with over 10 years of experience in the healthcare industry. I have a Master’s degree in Medicine, and my deep understanding of medical terminology, practices, and procedures has made me a trusted source of information in the medical world.