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Codeine Allergy: Reactions, Symptoms & What to Expect

Peter Manza, PhD profile image
Reviewed By Peter Manza, PhD • Updated May 13, 2023 • 5 cited sources
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A true codeine allergy is extremely rare. Most symptoms people attribute to allergies (like itching or nausea) are caused by entirely different processes. 

But if you’re one of the very rare people with a true codeine allergy, your dose could impair your breathing or cardiovascular health. This is a medical emergency that requires prompt treatment with epinephrine or steroids. 

How Common Are Codeine Allergies?

Very few people have true allergies to codeine. In fact, doctors say allergic reactions to opioids like codeine make up less than 2% of all hypersensitivity reactions in patients undergoing anesthesia.[1] 

Even though allergies are so rare, many people believe they have them. But doctors say as many as 9 patients in 10 labeled with an opioid allergy don’t have one at all.[2] 

People who claim they are allergic to codeine often reference one of the following symptoms:

  • Vomiting: Codeine can slow the digestive tract, prompting people to feel queasy. Sometimes, people vomit due to this action. Digestive upset isn’t a sign of codeine allergies. 
  • Hives: Opioids like codeine can cause the body to release histamine, a chemical used by the immune system.[3] When too much histamine is present, hives and itching develop. This symptom is uncomfortable, but it’s not caused by a true allergic reaction.
  • High blood pressure: Itchy skin is painful, and your heart can beat faster in response. This symptom isn’t caused by allergies. 

If you struggle with codeine side effects, you can tell your doctor about them and request a different therapy. But know that an allergic reaction doesn’t cause these three common problems. 

Signs & Symptoms of a Codeine Allergic Reaction

A true allergic reaction may look a lot like a pseudo-allergy response. You may develop hives, itching, flushing and a higher-than-normal blood pressure reading. But you may have other symptoms people without allergies don’t develop.

People with a true codeine allergic reaction develop the following symptoms:[4]

  • Very low blood pressure readings
  • Swelling in your tongue, lips, face or mouth 
  • Respiratory distress 

Since allergic reactions involve critical systems like your heart and lungs, you should go to an emergency room immediately. Bring your pills with you, and tell the doctor how much you took. 

How to Treat a Codeine Allergy

If you struggle to breathe after taking codeine, go to the emergency room. The team will assess your condition and determine what to do next.

If you took oral codeine pills, the team might suction contents from your stomach, preventing more codeine from passing through the digestive tract. They may also give you fluids to help your organs process any codeine in the bloodstream. 

Medical teams can use medications like epinephrine and steroids to treat an ongoing allergic reaction.[5] These drugs quickly soothe the central nervous system and stop painful symptoms before they worsen. 

A true allergic reaction is a medical emergency. It’s important to seek immediate help.

Alternatives to Codeine

If you’ve had a true allergic reaction to codeine, you shouldn’t take more. People with mild reactions may have better results with an opioid from another class. But those who had life-threatening reactions to codeine may not be willing or able to risk their health by using a similar drug.

Over-the-counter pain medications like aspirin don’t work like opioids, and they can be effective painkillers. If you’re struggling with mild pain, aspirin might be a better short-term solution.

If you have long-term, chronic pain, opioids may not be the best choice available. Some people find that physical therapy, massage or yoga are more effective methods of pain control, and they don’t come with the overdose risks attached to opioids. 

Ask your doctor about your solutions. Together, you can find a treatment plan that’s right for your body and your pain.

Reviewed By Peter Manza, PhD

Peter Manza, PhD received his BA in Psychology and Biology from the University of Rochester and his PhD in Integrative Neuroscience at Stony Brook University. He is currently working as a research scientist in Washington, DC. His research focuses on the role ... Read More

  1. Opioid-Free Anesthesia and Analgesia in a Patient with Opioid Allergy. Regional Anesthesia and Pain Medicine. 2019. Accessed March 2023.
  2. Opioids: Allergy vs. Pseudoallergy. U.S. Pharmacist. July 2006. Accessed March 2023.
  3. Absolute Contraindications to Opioid Prescribing. Utah Clinical Guidelines on Prescribing Opioids for Treatment of Pain. 2003. Accessed March 2023.
  4. Prescribing Opioids Safely in Patients With an Opiate Allergy. JAAPA. January 2012. Accessed March 2023.
  5. What Is a True Opioid Allergy? Practical Pain Management. January 2021. Accessed March 2023.
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