Codeine Allergy: Symptoms, Causes, and Allergy Management

What you will learn

• Codeine allergies are extremely rare, but codeine can cause a histamine reaction with allergy-like symptoms.
• Pseudoallergies with codeine have symptoms like hives and itching, while true codeine allergies can cause life-threatening complications like anaphylaxis.
• A true codeine allergy can cause allergic reactions to other opioid medications.

A drug allergy is an allergic reaction to a normally harmless substance in a medication. Some common drug allergies include sulfa drugs, penicillin, and nonsteroidal anti-inflammatory drugs (NSAIDs). Though rare, other medications, including codeine and other opiates, can cause drug allergies.

Learn more about codeine allergy, its symptoms, and what to do if you suspect you’re allergic to codeine-containing drugs.

What Is a Codeine Allergy?

A true codeine allergy is extremely rare. Often, symptoms commonly attributed to allergies, such as itching or nausea, are caused by a pseudoallergy effect caused by the body’s histamine response.

However, if you’re one of the few people with a true codeine allergy, taking codeine-containing drugs can cause life-threatening complications like anaphylaxis. This is a medical emergency and requires prompt intervention.

How Common Are Codeine Allergies?

Very few people have a true allergy to codeine. According to experts, allergic reactions to opioids like codeine account for less than 2% of all hypersensitivity reactions in patients undergoing anesthesia.[1]

Though codeine allergies are rare, it’s common for people to experience allergy-like symptoms that make them believe they have a codeine allergy. Opioids like codeine can cause the body to release histamine, leading to symptoms like itching.

Symptoms of a Codeine Allergy

A codeine pseudoallergy may have allergy-like symptoms, such as:[2]

• Itching
• Flushing
• Hives
• Sneezing
• Sweating
• Low blood pressure
• Worsening asthma

The symptoms of a true codeine allergy can be different and may include:[3]

• Low blood pressure
• Respiratory distress
• Swelling in the tongue, lips, face, or mouth
• Wheezing or coughing
• A rash that resembles pimples
• Hives
• Erythema multiforme (bullseye-shaped lesions)
• Swelling under the skin

Allergic reactions can affect vital systems in the body, including the heart and lungs. It’s best to seek emergency medical attention to avoid complications if you have any symptoms, including pseudoallergy symptoms.

What Causes Codeine Allergy?

True codeine allergies are caused by an immune response, like other drug allergies. If you have a codeine allergy, your immune system responds by making immunoglobulin E (IgE) after your first exposure. This antibody removes harmful substances from your body.

The body makes different IgE types to target specific allergens. The IgE travels to the cells that contain histamine (mast cells) in the muscle membranes, skin, gastrointestinal tract, and airways.[4] When you encounter the drug again, the IgE attaches to the allergen, and the mast cells release histamine and other chemicals, causing immediate allergy symptoms.

T-cells can also cause an allergic reaction. These white blood cells work to protect your body from infection. Your T-cells recognize that the drug is a foreign body and bind to it, causing a slower immune response that causes skin symptoms like hives or itching.[5]

Risks and Complications of Codeine Allergies

Both codeine allergies and pseudoallergies can have risks and complications that range from mild to severe. The biggest concern with a true codeine allergy is anaphylaxis, which is a severe and potentially life-threatening reaction that includes symptoms like swelling of the face or throat, severe difficulty breathing, rapid heartbeat, and a dangerous drop in blood pressure.[6] If you have a codeine allergy, you may have sensitivities to other opioid medications.

Otherwise, codeine may be responsible for several adverse effects, some of which are dangerous. The common side effects of opioids like codeine are dry mouth, constipation, nausea, vomiting, and mental confusion.

Regular use of codeine or other opioids can cause constipation as well. Some people may experience nausea or vomiting with initial opioid use, but it often subsides after a few days.

In high doses, opioids like codeine can cause addiction, toxicity, or an overdose. An opioid overdose can be life-threatening and requires emergency medical care. The symptoms of an opioid overdose include shallow breathing, confusion, low alertness, and loss of consciousness.[7]

If you suspect someone is overdosing on a codeine drug or another opioid, call 911 immediately. Administer naloxone if you have it and wait until help arrives. Rapid intervention is the best way to prevent complications from opioid toxicity.

Precautions to Take with a Codeine Allergy

If you have a psuedoallergic reaction to opioids with symptoms like sweating, hives, or itching, it’s best to reduce your opioid dose and administer an antihistamine. Pseudoallergic reactions occur as a combination of opioid dose and potency. A higher potency opioid given at a lower dose and frequency may help.[8]

If you need opioids and have adverse effects from codeine, opioids in a different structural class may be a suitable alternative, but this requires careful evaluation by a doctor or a pharmacist.[9] However, this requires careful monitoring to avoid allergy-like symptoms

If you have a true allergy to codeine or other opioid drugs, a synthetic opioid like fentanyl may be used as a substitute. This can help with allergy symptoms, but it comes with different risks. Because of fentanyl’s potency, which is 50 to 100 times that of morphine, fentanyl carries a significant risk of addiction and overdose.

Many alternatives to opioid medications may help with pain, such as acetaminophen or an NSAID.

How to Avoid Codeine-Containing Medications with a Codeine Allergy

If you have a true codeine allergy or experience severe effects from codeine, it’s best to avoid the drug altogether. Speak to your doctor and pharmacist about your allergy or pseudoallergic symptoms to ensure you’re not prescribed a drug that contains codeine or other opioids that are likely to cause a similar reaction.

You should check medication labels and package inserts for codeine or related ingredients. Some prescription cold medications or pain medications contain a combination of an NSAID or other drugs with codeine, so you could take codeine without realizing it.

A codeine allergy is an emergency, so wear a medical alert bracelet or carry an allergy card that lists your codeine allergy. This precaution can save your life if you’re in an emergency and can’t communicate your allergy to medical response teams.

Work with your healthcare provider to find alternative medications for pain management or cough relief that do not contain codeine or opioids with a similar structure. Ensure your pharmacist knows your allergy to ensure that codeine is not dispensed with your medications.

Be Mindful of Codeine-Containing Drugs

Codeine allergies are rare, but they can occur. Some people experience pseudoallergic symptoms from codeine, such as hives and a rash, but a true codeine allergy is a medical emergency. If you have a true codeine allergy, it’s best to avoid drugs that contain codeine.

Amanda is a prolific medical content writer specializing in eating disorders and addiction treatment. She graduated Magna Cum Laude from Purdue University with a B.S. in Social Work. Read more