Drug Allergy

A reaction of the immune system to a medicine is called a drug allergy. While any supplement, herbal product, over-the-counter (OTC) medicine, and prescription medicine can trigger a drug allergy, it usually occurs with specific medicines only.

Rash, fever, and hives are the most common drug allergy symptoms. However, this condition may cause serious health problems, including a life-threatening condition called anaphylaxis.

It is important to know that drug allergies are not side effects of medicines. In most cases, adverse reactions to medicines are listed on their labels. Furthermore, drug allergy is also different from drug toxicity. When a person takes high doses of a medicine, drug toxicity may occur.

Symptoms

In most cases, drug allergy symptoms occur within 60 minutes after taking the medication. However, other symptoms, such as rash, may occur days or weeks later. Check below for some drug allergy symptoms:

Fever
Swelling
Shortness of breath
Runny nose
Itchy and watery eyes
Wheezing
Itching
Hives

Anaphylaxis Symptoms

Get emergency help if this life-threatening condition occurs. While anaphylaxis occurs quite rarely, it may be fatal. Check below for some symptoms:

Dizziness
Lightheadedness
Hypotension (low blood pressure)
Slow or fast heartbeats
Seizures
Loss of consciousness
Vomiting
Nausea
Diarrhea
Abdominal (belly) cramps
Breathing problems

Causes

Drug allergies occur when immunity mistakenly identifies a medicine as a harmful substance (such as bacteria or viruses). However, if it identifies the medicine as something harmful, it begins to produce antibodies that attack this medicine and cause allergy symptoms. Sometimes, a drug allergy may occur until repeated exposures to that medicine occur. In other words, the next time you take the medicine, the immune system will begin to attack it, causing allergic reactions.

Sometimes, people are not aware of their first exposure to the medicine because even a small amount of medicine in the food supply may cause the immune system to produce antibodies.

Experts believe that certain medications may bind directly to certain immune system cells (T cells), causing the release of certain chemicals that lead to allergic reactions. This may occur even if you are taking a specific medicine for the first time.

Medicines Usually Linked to Allergies

While all medications may cause an allergy, the following ones are more commonly linked with allergies. For example:

Antibiotics (such as Penicillin)
Other-the-counter (OTC) pain relievers (including Aspirin, Ibuprofen, Naproxen Sodium, and others)
Chemotherapy drugs (medicines used to treat cancer)
Medications used to treat autoimmune diseases (such as rheumatoid arthritis)

Nonallergic Medicine Reactions

In some cases, people may develop a condition called nonallergic hypersensitivity reaction or pseudoallergic drug reaction. It causes symptoms similar to a drug allergy, but they are not caused by an immune system reaction. Check below for some medications usually associated with this condition:

Opiates (used to treat severe pain)
Local anesthetics
Aspirin
Radiocontrast media (also known as dyes used in imaging tests)

Risk Factors

Anyone may develop a drug allergy. However, there are some factors that may elevate your risk of developing it. For example:

Medical or family history of drug allergies
Other allergies (including hay fever, food allergy, and others).
High doses of medicine used for long periods
Certain infections are usually associated with drug allergy reactions (such as HIV infection, Epstein-Barr virus infection, and others)

How to Prevent Drug Allergy?

Commonly, to prevent drug allergy, you should interrupt using the medication that causes problems. Check below for some tips that may help protect yourself:

Talk with your healthcare professional about allergic reactions you experience.
You should also wear a medical alert bracelet that helps identify medicines that cause allergies.

Diagnosis

It is very important to have an accurate diagnosis. Moreover, some research has shown that drug allergies may be misdiagnosed and that patients may report drug allergies that were never confirmed. In addition, misdiagnosed drug allergies may lead to the use of less appropriate or more expensive medications.

In most cases, physicians perform a physical examination and ask some questions about your symptoms, medicines you are using, and others to diagnose the condition. They may also perform some tests to confirm the condition and rule out others that cause similar symptoms. For example:

Skin test – During this test, doctors will administer a small amount of medicine that is suspected to cause a drug allergy to the skin. If you experience within a few minutes red, itchy, and raised bumps, it indicates a drug allergy. However, a negative outcome does not mean drug allergies are not possible. It usually means that you do not have allergic reactions to the medicine administered to your skin.
Blood tests – These tests are done to exclude other diseases that cause similar symptoms.

Treatment

In most cases, treatment for drug allergies is divided into two categories, such as treatment for present symptoms of the allergy and treatment that allows taking allergy-causing medications when it is necessary.

Treatment for Present Symptoms

These include:

Stop using the allergy-causing medicine – If doctors identify the exact medicine that causes allergy, they may recommend reducing the dose or even stopping it. If this medicine is necessary, physicians may recommend drug desensitization or change medicine.
Antihistamines – Physicians may prescribe these medicines or recommend an over-the-counter antihistamine (such as Diphenhydramine) to block the immune system reaction.
Corticosteroids – These medicines are available as a shot or taken orally (tablets or capsules). Corticosteroids are used to lessen symptoms linked with severe allergic reactions.
Anaphylaxis treatment – This life-threatening condition requires an immediate shot of Epinephrine. Moreover, people who have anaphylaxis need to stay several days in the hospital to maintain blood pressure and support breathing.

Treatment for Allergy-causing Medications

Usually, physicians do not prescribe allergy-causing medications unless it is needed in people with drug allergies. However, if the suspect medication is necessary, you should take it under medical supervision, but if the medicine causes severe or life-threatening symptoms, doctors will try to find another medicine next time.

What is Drug Desensitization?

This treatment involves taking very small doses of the allergy-causing medicine and then increasing the dose gradually every 15-30 minutes. Therefore, if you do not have allergic reactions over a few hours or days, you can continue the treatment. In addition, this treatment option is called drug desensitization.

Frequently Asked Questions

What are the primary symptoms of drug allergy?

For example:

Itching
Skin rash or hives
Swelling
Trouble breathing
Wheezing
Anaphylaxis (a life-threatening condition that requires immediate treatment in the hospital)

If any of the previous symptoms occur, immediately contact your healthcare provider.

What is the most common drug people are allergic to?

Mostly, people develop a drug allergy to an antibiotic called Penicillin. However, there are a lot of people who are allergic to over-the-counter (OTC) pain relievers such as Aspirin, Ibuprofen, and others.

What are the potential complications of drug allergy?

People with this condition may experience some complications, especially if they ignore the symptoms and do not get treatment. For example:

Anaphylaxis
Serum sickness
Anemia
Kidney inflammation

Ask your healthcare provider if you have additional questions.