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A Comprehensive Guide to Medicine Allergies

Team AckoDec 11, 2023

What is Medicine Allergy?

Medication allergy is the unusual response of your body to any type of medicine. A herbal supplement, a prescription drug, or over-the-counter medicines, any of these may give you a drug reaction. Not all drug allergy symptoms are serious, and may subside once you stop the medicine. However, some drug allergies can harm multiple organ systems in the body and prove to be life-threatening. Discussed below are a few reasons behind what might cause these allergies.

Medicine Allergies



What Causes Drug Allergies?

In normal circumstances, the body's defence mechanism, called the immune system, fights any harmful organisms in the form of bacteria, viruses, and other microorganisms. In the event of a medicine allergy, your immune system mistakes the particular medicine as an intruder. Considering it to be harmful, it becomes sensitised against the medication and produces antibodies to fight against it. Antibodies are proteins that assault this invader, giving rise to various drug allergy symptoms, including inflammation, fever, skin rash, breathing difficulties, etc. This type of immune sensitisation may occur when you take the drug for the first time, or it might also happen after you have taken the drug multiple times.

Difference Between Drug Allergy and Side Effects

Many mistakenly consider the side effects of a medication to be medication allergy; however, the two are entirely different. Side effects of a medication are known as effects caused by the drug for which it might not have been intended, and these are listed on the label. These can happen to any individual taking a medicine and aren't usually triggered by the immune system. Drug allergies also differ from the drug toxicity that occurs if you overdose on the medication.

What Predisposes You to Have Drug Allergies?

Anyone can experience medication allergy at any point in time; however, some factors predispose you to these allergies. Some of these risk factors are as follows:

  • Personal history of food allergies, dust and pollen allergies, hay fever, etc.

  • Anyone in the family with drug allergies.

  • Using a medicine over a long period or in high doses.

  • Diseases where the immune system is compromised, include Epstein-Barr virus infection or HIV infection.

Drugs That Most Commonly Cause Allergies

Certain drugs are more likely to cause allergies more than others. These drugs include:

  • Aspirin

  • Chemotherapy drugs

  • Certain antibiotics such as penicillin, amoxicillin, etc.

  • Anti-inflammatory medicines (Nonsteroidal)

  • Sulfa drugs

  • Drugs used to treat HIV

  • Insulin

  • Muscle relaxants (given by IV)

  • Anti-seizure/ anticonvulsant drugs

  • Monoclonal antibody therapy drugs

Apart from the drug, the method of taking medicine also plays an important role here. You are more likely to get a drug allergy if you:

  • Take the medication as an injection and not orally.

  • Apply locally on your skin.

  • Take the medicine very frequently.

Drug Allergy Symptoms

You may experience certain drug allergy symptoms within a few hours of taking it. Following are the signs to watch out for:

  • Skin rash

  • Hives

  • Itchy, watery eyes

  • Fever

  • Inflammation or swelling

  • Shortness of breath 

  • Heavy breathing

  • Cold

  • Congestion

  • Nausea and vomiting

  • Lightheadedness

Sometimes, the reaction may be severe and can lead to anaphylaxis, a life-threatening situation. Following are its symptoms which might indicate this:

Some of the following symptoms may occur after some weeks of taking the drug:

  • Nephritis

  • Serum sickness

  • Aplastic anaemia

  • DRESS (Drug Rash with Eosinophilia and Systemic Symptoms) 

Diagnosing Medicine Allergy

Diagnosing a medication allergy is much more difficult than often thought. A medicine allergy test is available only for penicillin-type drugs in the form of a skin test or patch test for some antibiotics and anticonvulsants. Your healthcare provider may prescribe this test if he suspects a penicillin reaction.

Your doctor does a thorough history and physical examination to look for the symptoms. He will ask you about previous such occurrences, if any. He may ask about the allergy history of other family members and other such questions. He may order some blood tests if the involvement of some vital organs is suspected.

Sometimes the specialist may order a 'challenge,' which means you are asked to take the suspected allergy-causing medicine again, but under medical supervision to check for any adverse reactions. However, a 'challenge' test is not considered safe if you have a severe or fatal drug reaction.

Treatment of Drug Allergy

Treatment and management of medication allergy depend on its severity. If you are severely allergic to a certain drug, it has to be completely avoided and replaced with a medicine you aren't allergic to.

If you are mildly allergic to a drug, the doctor may still prescribe it, along with another medicine, to help control the reaction. These medicines block the immune response, thereby reducing the symptoms. Following medications may be given to combat drug allergies:


Histamine is produced by the body when it thinks a substance or an allergen is harmful. The release of histamine may cause symptoms such as inflammation, itching, or irritation. Hence, antihistamines may be given to block the production of histamine and calm the symptoms. They can be taken in the form of pills, eye drops, nasal sprays, or creams.


Corticosteroids aid in reducing the inflammation of the airways and throat caused due to an allergic reaction. It can be given as an injection, inhaler, or nebuliser. They can also be used as pills, creams, or eye drops.


Drug allergies that cause wheezing and coughing mostly require a bronchodilator to open the airways, making breathing easier. They come in liquid and powder form to be used in an inhaler or nebuliser.

Tips for Drug Allergy Prevention

If you have a drug allergy, you must take the following steps to prevent further such episodes:

  • Inform your healthcare provider about any drug allergy before you take any type of treatment or undergo surgery, including dental surgeries.

  • Wear a medical device or carry a health card that displays your crucial health information.

  • Ask your doctor about medicines you must avoid and alternatives to them if any.


Medicines, health supplements, and herbal medications are usually beneficial for your body and help you cure diseases, and offer several health benefits. But sometimes, these can result in drug allergies, especially if your immune system goes into overdrive and perceives it as an invader.

Typically, medication allergies tend to settle down once you stop the culprit drug, but sometimes the reaction is severe and life-threatening, leading to hospitalisation. This type of medication allergy is called anaphylaxis which can affect multiple organs in your body, and may prove fatal if no corrective action is taken immediately.

Nonetheless, your doctor can treat and manage these allergies through various modalities. He can also help you prevent further drug allergy episodes by suggesting changes in your drug regimen.


Which drug has the maximum chance of causing an allergic reaction?


Many drugs may result in allergic reactions, such as aspirin, antibiotics, and chemotherapy drugs; however, penicillin is known to cause the maximum number of allergic reactions.

Which body system is involved in triggering a drug allergy?


An over-sensitive immune system causes drug allergy as it may perceive the medicine as harmful to the body. It releases proteins in the form of antibodies that try to destroy the drug, leading to allergic symptoms.

How long does it take an allergic reaction to occur?


After taking a medicine, a person may develop an allergic reaction within 12 hours; however, anaphylactic reactions can develop within minutes of drug intake.

How long do the drug allergy symptoms last?


It may take up to two weeks to completely recover from a drug allergy; however, the severity of symptoms is a deciding factor in the recovery period. Also, elderly people and immunocompromised individuals may require more time to recover from it.

Are there any specific tests for drug allergies?


There are three types of drug allergies usually prescribed by doctors-

  • A skin test to diagnose penicillin allergy.

  • A patch test to know if you are allergic to some antibiotics or anticonvulsant drugs.

  • Blood tests to diagnose other drug allergies.




Disclaimer: The content on this page is generic and shared only for informational and explanatory purposes. It is based on several secondary sources on the internet. As this content piece is not vetted by a medical professional, please consult a doctor before making any health-related decisions.


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