A codeine allergy is rare, but unpleasant pseudoallergy side effects are more common. If you are truly allergic to codeine, your doctor may recommend an alternative.

Having a codeine allergy is a problem some people face, making them unable to take the prescription opioid for pain or treat a cough. The following overview covers what codeine is, what a codeine allergy reaction is like and alternative options that may be available.

Article at a Glance:

  • A codeine allergy is rare. More often than not, the symptoms people experience that they think are related to a codeine allergy are just normal symptoms of the drug caused by their body’s histamine response.
  • If you have a codeine allergy, you should not take codeine. You should contact your doctor if you suspect a codeine allergy.
  • If you are truly allergic to codeine, your doctor may recommend an alternative to codeine.

Is It a Codeine Allergy?

Some of the general side effects of codeine can include feeling dizzy or lightheaded, nausea, vomiting, shortness of breathing, sedation, constipation and itchy skin. There are also serious but rare side effects possible, like respiratory depression and severely low blood pressure.

Some people may also experience an allergic reaction to codeine. While possible, many people think they have a codeine allergy when they’re really only experiencing the side effects of the drug itself. For example, itchy skin is a common opioid side effect but does not indicate a codeine allergy. Nor are other symptoms commonly associated with allergies, like blurred vision or constipation. These are all just expected side effects of using codeine.

How Common Are Codeine Allergic Reactions?

A true codeine allergic reaction is pretty rare. In up to 90% of cases, a person who thinks they have an allergy to an opioid does not actually have a true allergy.

In most cases, doctors describe what’s perceived as a codeine allergic reaction as being a pseudoallergy instead. Codeine pseudoallergies are allergic symptoms due to the histamine released from your cells, while true codeine allergies come from an immune system reaction. Codeine is one of the opioids most commonly associated with pseudoallergies.

Pseudoallergy symptoms include:

  • Flushing
  • Itching
  • Sneezing
  • Hives
  • Sweating
  • Asthma exacerbation
  • Low blood pressure

Signs of an Allergic Reaction to Codeine

True codeine allergy symptoms are caused by the immunoglobulins or T-cells in your immune system.

Symptoms of a codeine allergy include:

  • Hives
  • A rash that looks like discolored, bumpy skin
  • A rash that looks like pimples
  • Blisters
  • Swelling of the mouth, neck or face
  • Severely low blood pressure
  • Trouble breathing

What To Do if You’re Having an Allergic Reaction to Codeine?

If you believe you are having an allergic reaction to codeine, it is important to seek medical attention right away. An allergy can lead to trouble breathing, which can be fatal. If you have been diagnosed with a codeine allergy and have accidentally taken the drug, you should use your epinephrine (EpiPen) auto-injector and seek emergency medical attention.

Although itchy skin is a common side effect of opioids, occurring in up to 10% of people, a rash is not common. Because a rash can be due to a codeine allergy, seek medical attention if you develop a rash while taking the drug. Drug allergies do not usually go away on their own, so it is important to rule out a true allergy before continuing to take codeine. Your doctor will ask you questions about the rash and when it occurred, and they may want to physically examine the rash before telling you if it is safe to continue taking codeine.

Related Topic: Alcohol allergy rash treatment

Drug Interactions

Although drug interactions cannot cause a codeine allergy, they can enhance codeine’s side effects.

Drugs that interact with codeine and can worsen its side effects include:

  • Alcohol
  • Benzodiazepine drugs like lorazepam (Ativan), diazepam (Valium), and alprazolam (Xanax)
  • Cannabis, including cannabidiol (CBD) products
  • Other opioids
  • Anticholinergic drugs that impact acetylcholine in the body, like amitriptyline and oxybutynin
  • Kava kava
  • Monoamine oxidase inhibitors (MAOIs) like selegiline (Emsam, Zelapar)
  • Sleep drugs, like zolpidem (Ambien)

Alternatives to Codeine

Unfortunately, most opioids that are similar to codeine in potency also have a similar chemical structure to codeine. Most oral opioids have a phenanthrene chemical structure, and an allergy to one may cause an allergy to the rest. One exception is the atypical opioid tramadol, which is a synthetic opioid and not a phenanthrene. If you are allergic to codeine, your doctor may instead prescribe tramadol. Alternatively, your doctor may recommend non-opioid pain relievers, like acetaminophen or non-steroidal anti-inflammatory drugs (NSAIDs) like ibuprofen.

Other more potent opioids that are not phenanthrenes include methadone and fentanyl. However, given codeine’s low potency and the high potency of methadone and fentanyl, these drugs are not likely to be prescribed as a replacement for a person allergic to codeine.


What is codeine?

Codeine is a prescription opioid that is given to patients to treat pain or cough. It’s considered one of the milder narcotic pain relievers, but it’s not without risk.

If I am allergic to codeine, what can I take for pain?

If you are allergic to codeine, your doctor may recommend a chemically unrelated opioid like tramadol. Alternatively, your doctor may recommend non-opioid pain relievers, like acetaminophen or an NSAID like ibuprofen.

Can you take oxycodone if allergic to codeine?

If you have a true codeine allergy, it’s likely you can’t take oxycodone. Both oxycodone and codeine are phenanthrene opioids and have a similar chemical structure. This means that your body may react to them in the same way, including an allergic reaction.

Can you take hydrocodone if allergic to codeine?

It’s likely you won’t be able to take hydrocodone if you have a true codeine allergy. Both hydrocodone and codeine are phenanthrene opioids. This means that they share a similar chemical structure. As a result, your body may react to them in a similar way, meaning that an allergic reaction to one can cause allergic symptoms in the other.

Is codeine addictive?

While less potent than many other opioid narcotics, codeine can be habit-forming. As a controlled substance, codeine can cause physical dependence after a person takes it for a longer period of time. Physical dependence means a person will experience symptoms of withdrawal if they suddenly stop.

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Editor – Melissa Carmona
Melissa Carmona puts years of writing and editing experience to work helping people understand substance abuse, addiction and mental health disorders. Read more
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Medically Reviewed By – Dr. Jessica Pyhtila, PharmD
Dr. Jessica Pyhtila is a Clinical Pharmacy Specialist based in Baltimore, Maryland with practice sites in inpatient palliative care and outpatient primary care at the Department of Veteran Affairs. Read more

Drugs.com. “Codeine.” October 30, 2020. Accessed May 31, 2021.

Drug Enforcement Administration. “Controlled Substances.” May 10, 2021. Accessed May 31, 2021.

American Academy of Family Physicians. “Opioid Conversion Table.” Accessed May 31, 2021.

Saljoughian, Manouchehr. “Opioids: Allergy vs. Pseudoallergy.” U.S. Pharmacist, July 20, 2006. Accessed May 31, 2021.

Bigliardi, Paul L.; Bigliardi-Qi, Mei. “Peripheral Opioids.” Itch: Mechanisms and Treatment, 2014. Accessed May 31, 2021.

American College of Allergy, Asthma, and Immunology. “Drug Allergies.” February 28, 2018. Accessed May 31, 2021.

Medical Disclaimer

The Recovery Village aims to improve the quality of life for people struggling with substance use or mental health disorder with fact-based content about the nature of behavioral health conditions, treatment options and their related outcomes. We publish material that is researched, cited, edited and reviewed by licensed medical professionals. The information we provide is not intended to be a substitute for professional medical advice, diagnosis or treatment. It should not be used in place of the advice of your physician or other qualified healthcare providers.