Drug Allergy

Your body's immune system can react to a medication, and that's called a drug allergy. This can happen with any kind of medicine, whether you get it over the counter, from a doctor, or from a natural source like herbs. Some medicines are more likely to cause a reaction than others.

Common signs of a drug allergy include itchy skin (hives), a skin rash, and a fever. But a drug allergy can also cause much more serious problems, like anaphylaxis. Anaphylaxis is a very serious, potentially life-threatening reaction.

A drug allergy is different from a medicine's side effects. Side effects are known, expected reactions that a medicine might cause. These are usually listed on the medicine's label or packaging. A drug allergy is also different from medicine poisoning. Medicine poisoning happens when you take too much of a medicine.

Taking medicine can sometimes trigger allergic reactions. These reactions can show up quickly, within an hour, or they might develop later, after a few hours, days, or even weeks. Common signs of a drug allergy include:

• Skin problems: A rash, hives (raised, itchy bumps), and itching are common.
• Body-wide symptoms: Fever, swelling, trouble breathing (shortness of breath or wheezing), a runny nose, and itchy, watery eyes can also occur.

A serious allergic reaction, called anaphylaxis, is rare but can be life-threatening. It causes your body to react strongly, affecting many systems. Symptoms of anaphylaxis include:

• Breathing problems: Your throat and airways might tighten, making it hard to breathe.
• Stomach problems: Nausea, stomach cramps, vomiting, or diarrhea.
• Circulatory issues: Dizziness, lightheadedness, a fast and weak pulse, and a drop in blood pressure.
• Other serious symptoms: Seizures and loss of consciousness.

Sometimes, allergic reactions to medicine develop more slowly, appearing days or weeks after you take the medication and lasting even after you stop taking it. These delayed reactions include:

• Serum sickness: This can cause fever, joint pain, a rash, swelling, and nausea.
• Drug-induced anemia: This is a decrease in red blood cells, leading to fatigue, irregular heartbeats, shortness of breath, and other symptoms.
• Drug rash with eosinophilia and systemic symptoms (DRESS): This condition involves a rash, a high white blood cell count, swelling throughout the body, swollen lymph nodes, and sometimes a hepatitis infection that comes back after it seemed to disappear.
• Kidney inflammation (nephritis): This can cause fever, blood in the urine, swelling, confusion, and other symptoms.

If you think you're having a severe reaction or suspect anaphylaxis after taking medication, immediately call 911 or your local emergency number. For milder symptoms, see a doctor or other healthcare provider as soon as possible. It's important to get medical attention quickly for any suspected drug allergy.

If you have a bad reaction to a medicine, call 911 or your local emergency number right away. This is especially important if you think you might be having a severe allergic reaction, sometimes called anaphylaxis. Anaphylaxis can be life-threatening.

If you have less serious symptoms of a medicine allergy, such as a rash or itching, see a doctor or other healthcare provider as soon as you can. Early treatment is important for managing these kinds of reactions.

A drug allergy happens when your body's immune system, which fights off germs, mistakenly sees a medicine as a threat. Think of it like your body recognizing a harmless medicine as a dangerous virus or bacteria. Your immune system creates special proteins called antibodies that are specifically designed to attack this "threatened" medicine. This can happen the first time you take a medicine, or it might take repeated exposure for an allergy to develop.

When you take the medicine again, these antibodies recognize it and signal your immune system to attack. This attack releases chemicals that cause the symptoms of an allergic reaction, like hives, itching, swelling, or trouble breathing.

It's possible to develop an allergy even if you haven't taken the medicine directly. Sometimes, small amounts of medicine can be found in food. If enough of these trace amounts are present, your immune system might still produce antibodies to that medicine.

Sometimes, a different process is at play. Scientists believe that some medicines can directly activate a type of immune cell called a T cell. This activation causes the release of chemicals that trigger an allergic response, even the first time you take the medicine.

Any medicine can potentially cause an allergic reaction, but certain types are more often linked to them. These include:

• Antibiotics: Like penicillin.
• Pain relievers: Such as aspirin, ibuprofen (like Advil or Motrin), and naproxen (like Aleve).
• Cancer treatment drugs (chemotherapy): Used to fight cancer.
• Medicines for autoimmune diseases: Like those used for rheumatoid arthritis.

Sometimes, the symptoms you experience after taking a medicine might seem like a drug allergy, but they aren't. Your immune system isn't involved. This is called a non-allergic hypersensitivity reaction or pseudoallergic drug reaction. These reactions can be caused by:

• Aspirin.
• Dyes used in medical tests (radiocontrast media): Used in X-rays and other imaging.
• Pain medications (opioids): Used to manage pain.
• Local anesthetics: Used to numb areas of the body during procedures.

It's important to note the difference between a true drug allergy and a pseudoallergic reaction, as the treatment and management approaches are different. If you suspect you have a drug allergy or a reaction to a medicine, it's crucial to talk to a doctor. They can properly diagnose the issue and recommend the best course of action.

Many people can have an allergic reaction to medicine. However, some things make it more likely. For example:

• A history of other allergies: If you've had allergies like food allergies or seasonal allergies (hay fever), you might be more prone to a drug allergy. This is because your immune system is already sensitive and more likely to react to something new.

• Family or personal history: If you or someone in your family has had a drug allergy before, you might be at higher risk. Your genes can play a role in how your immune system reacts.

• How often and how much medicine you take: Taking a medicine in high doses, repeatedly, or for a long time can increase your risk of an allergic reaction. Your body might develop a sensitivity over time.

• Certain infections: Some infections, such as HIV or Epstein-Barr virus, have been linked to drug allergies. These infections can sometimes trigger a reaction in your immune system that leads to an allergic response to a medicine.

If you're allergic to a medicine, the best way to stay safe is to avoid that medicine. Here's how to protect yourself:

Tell your doctors: Make sure your medical records clearly show you have a drug allergy. Tell all your healthcare providers about it, including dentists and other specialists. This way, everyone who treats you knows about your allergy.

Wear a medical alert bracelet: A bracelet that says you have a drug allergy can help save your life in an emergency. This lets medical professionals know right away, so they can give you the correct treatment.

Getting the right diagnosis for drug allergies is very important. Studies show that some people might be told they have a drug allergy even when they don't, or they might report an allergy that hasn't been proven. This can lead to using the wrong medicine or a more expensive one.

Doctors usually start by examining you and asking questions about your symptoms. Important details include when your symptoms started, when you took the medicine, and whether your symptoms got better or worse. This information helps them figure out what's going on.

If more information is needed, your doctor might order more tests or send you to a specialist called an allergist. Allergy tests can involve different methods.

One common test is a skin test. The allergist or a nurse puts a tiny amount of the suspected medicine on your skin, either by scratching the skin, injecting it, or using a patch. If you have a reaction, like a red, itchy bump, it could suggest an allergy.

A positive skin test result suggests you might have a drug allergy. However, a negative skin test isn't always clear-cut. For some medicines, a negative test usually means you aren't allergic. But for others, a negative test might not completely rule out the possibility of an allergy.

Blood tests can also help rule out other health problems causing your symptoms. While blood tests exist to check for some drug allergies, they aren't commonly used. This is because there isn't a lot of research showing how accurate they are. Blood tests might be considered if there's a concern about a serious reaction to a skin test.

Based on your symptoms and the test results, the doctor can usually reach one of these conclusions:

• You have a drug allergy.
• You don't have a drug allergy.
• You might have a drug allergy, but the likelihood is unclear.

These conclusions are important for making decisions about your future treatment.