I think I have an allergy to my antibiotic! What can I do to treat my infection?
Introduction
Antibiotics are a safe and effective way to treat many bacterial infections. You or someone you know may have experienced an unpleasant reaction after taking an antibiotic, such as diarrhea or a rash. How can you tell if this is an allergic reaction or a side effect from the medication? Does this mean that you can never take that antibiotic again?
How do I know if I am having an allergic reaction to my antibiotic?
True allergic reactions are actually not very common with antibiotics. Allergies happen when your body's defense system overreacts to a medication. Some reactions may occur right away—within minutes to hours—while others may take over a day or a week to appear.
Allergic reactions can manifest as an itchy rash, hives (raised bumps), facial swelling, tightness in the throat, wheezing, and coughing. In some cases, symptoms can be more severe and include trouble breathing, dizziness, or fainting, or swelling of the tongue, nose, throat, and lips. If any of these symptoms occur, seek emergency medical care immediately.
Side effects are common with antibiotics and are different from allergies. They can include feelings of nausea, vomiting, diarrhea, upset stomach, headaches, dizziness, and muscle pains. If you experience a side effect from an antibiotic, it does not necessarily mean you have to stop taking the medication. Adjusting the dose or treating your unwanted symptoms with your doctor's guidance can help.
What is the most common antibiotic allergy?
The most common antibiotic allergy is to penicillin. Interestingly, about 80% of people who are allergic to penicillin outgrow their sensitivity after 10 years. Your penicillin allergy of today may fade away in the future.
Related questions
- What are the best antibiotics for pneumonia?
- What causes black hairy tongue?
- How long do antibiotics take to work?
I had an allergic reaction to an antibiotic in the past. What are my options if I get an infection?
If you have experienced an allergic reaction to an antibiotic before and need medication for an infection, there are other safe and effective options. If you are allergic to penicillin, your doctor can prescribe a cephalosporin, an antibiotic in a similar class of medication but different enough in its chemical makeup to avoid a reaction. Other classes of antibiotics, such as macrolides and tetracyclines, may also be an option to treat an infection without causing an allergic reaction.
A process called desensitization is another option for patients with a penicillin allergy, but requires additional treatment. It is a process of giving an antibiotic in gradual doses to allow a person to temporarily tolerate the medication and reduce the chance of a reaction. It must be done under close supervision of a doctor.
Summary
Experiencing a side effect from an antibiotic does not necessarily mean you have an allergy. If you develop symptoms and are concerned about a reaction, your doctor or pharmacist can help and will advise you if you need to stop the medicine.
You should not completely stop a medicine without seeking the advice of a doctor or pharmacist, even if your infection symptoms are better, as stopping the antibiotic early may prevent the antibiotic from working for you again in the future. If you do have an allergy to an antibiotic, there are many options available to you for treating an infection in the future. Your doctor or pharmacist can help determine which option is best for you.
Related medical questions
- Meloxicam vs Ibuprofen: What's the difference?
- Aleve vs Ibuprofen: What's the difference?
- Can you take expired ibuprofen?
- What's the difference between aspirin and ibuprofen?
- Can you overdose on ibuprofen?
- Does gabapentin help treat nerve pain?
- Can you take tramadol with acetaminophen, ibuprofen, or aspirin?
- Can you drink alcohol with ibuprofen?
- How do Celebrex and ibuprofen compare?
- Acetaminophen vs paracetamol: What do you need to know?
- Should I take meloxicam at night or in the morning?
- Acetaminophen vs Ibuprofen: Which is better?
- Oxycodone vs Hydrocodone - How do they compare?
- Tylenol vs Advil: What's the difference?
- How long can you take Celebrex for?
- Why does my child have leg pain or trouble walking after a fever?
- What is Metamizole used for?
- CBD Oil: What are 9 Proven or Possible Health Benefits?
- Which painkiller should you use?
- What are the rules for controlled substance prescription refills?
- Can you take ibuprofen 800 mg with tramadol 50 mg?
- How much Tylenol can you take in a day?
- Aleve vs Advil: What's the difference?
- Motrin vs Advil: What's the difference?
- Can ibuprofen cause constipation?
- How long does ibuprofen take to work?
- How long does oxycodone stay in your system?
Drug information
- Tetracycline Information for Consumers
- Tetracycline prescribing info & package insert (for Health Professionals)
- Side Effects of Tetracycline (detailed)
- Tetracycline user reviews (64)
Related support groups
- Penicillin (105 questions, 111 members)
- Tetracycline (11 questions, 40 members)
- Pain (2,280 questions, 11,939 members)
- Infections (616 questions, 992 members)
- Nausea/Vomiting (450 questions, 926 members)
- Headache (420 questions, 1,467 members)
- Diarrhea (215 questions, 395 members)
- Allergic Reactions (222 questions, 469 members)
- Allergies (169 questions, 462 members)
- Muscle Pain (167 questions, 573 members)
- Skin Rash (140 questions, 446 members)

AHFS® Patient Medication Information is used with permission. ©2025, the American Society of Health-System Pharmacists, Inc. (ASHP). The ASHP Data is a part of the AHFS Drug Information®️; ASHP is not responsible for the accuracy of transpositions from the original context.