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Opioid Allergy or Something Else?


It is common for a person to assume they are suffering from an allergic reaction when they experience a drug’s negative side effects. Considering the number of potential aftereffects that each new substance can result in, it makes sense that the waters of what counts as an allergic reaction or not can get quite muddied over time. In the case of opioid prescriptions, many patients will experience unpleasant sensations as their doctor determines which medication will be most effective in their unique case. This is when their physicians must practice discretion between what is truly an opioid allergy and what is a pseudoallergic reaction.  

What Is a Pseudoallergic Reaction? 

A pseudoallergy refers to when a patient illustrates similar clinical symptoms to a typical allergic reaction but without the presence of IgE antibodies.1 These antibodies are usually responsible for the symptoms someone experiences during an allergy attack and are produced as the immune system overreacts to a specific allergen.2 The main indicator between an allergy and a pseudoallergy is the presence or lack of these antibodies. 

How Common Is an Opioid Allergy? 

Despite the frequency with which patients will assert they are having a reaction to their opioid prescription, the reality is that only 2% of these are true allergies.3 In the other 98%, it is, in fact, much more likely that they are experiencing side effects. It is crucial for physicians to dig deeper into what may be causing an adverse effect because assuming that a true allergy is occurring can lead to delays in treatment and unnecessary substance avoidance.  

It is possible for all opioids to produce allergic reactions, although it is most observed in cases where codeine, morphine, and meperidine are prescribed. What can get confusing is the fact that some pseudoallergic symptoms can mimic those of a true allergy. What separates the two is the release of histamine from mast cells.  

This release can result in several symptoms, including: 

  • Asthma attacks or difficulty breathing 
  • Flushing of the skin 
  • Hives and itching 
  • Low blood pressure 
  • Sneezing 
  • Sweating 

Chronic opioid use can also play a part in the development of unwanted symptoms and side effects. Aside from the very real prospect of abuse and addiction, a person can struggle with many other physical consequences that stay with them for the rest of their life. 

Diagnosis of an Opioid Allergy 

It is crucial for doctors to be able to distinguish between allergic and non-allergic patients. They should not seek to withhold a certain medication if the cause of an adverse reaction is unclear. That said, if the patient’s condition is determined to be opioid-related, their physician can reference their medical history to select a safer alternative. Other factors to keep in mind include eating habits, the symptoms themselves, and any other drugs the patient ingested before their onset of symptoms. 

It is also crucial for doctors to educate their patients about all potential side effects of their prescribed opioid. Common side effects include:  

  • Dry mouth 
  • Confusion 
  • Nausea 
  • Vomiting 
  • Constipation 

While these are considered adverse effects, they are not necessarily an allergy and can be managed without removing the prescription. Also, pharmacists can play a role in evaluating symptoms that a patient is experiencing. While dispensing the medication, they can collect valuable information on the physical well-being of the patient and act as a resource to other members of the medical team.4 Each person has a role to play in helping a person find the best solution for what they are struggling with.  

Do Not Struggle Alone  

The world of drugs is an extremely complex one that is ever-changing with the continual development of modern medicine. This is something Banyan’s Chicago addiction treatment center professionals are aware of. Should you find yourself struggling because of an opioid prescription turned addiction, we can help. We offer substance-specific addiction treatment that can comprehensively address what you are experiencing, while our vast collection of therapies can teach you healthier coping mechanisms moving forward. 

To learn more about our programs for Illinois addiction treatment, call Banyan at 888-280-4763 today.  



  1. Clinical Trials.gov - The Clinical Study on Pseudo-allergic Reaction to Anesthetic Drugs During General Anesthesia 
  2. AAAAI - Immunoglobulin E (IgE) Defined 
  3. Pharmacy Times - Opioid Allergy, Pseudo-allergy, or Adverse Effect? 
  4. US Pharmacist - Opioids: Allergy vs. Pseudoallergy 


Related Reading 

Opioid Addiction in the Elderly 

Opioid Addiction After Surgery 

Alyssa, Director of Digital Marketing
Alyssa, Director of Digital Marketing
Alyssa is the National Director of Digital Marketing and is responsible for a multitude of integrated campaigns and events in the behavioral health and addictions field. All articles have been written by Alyssa and medically reviewed by our Chief Medical Officer, Dr. Darrin Mangiacarne.
Opioid Allergy or Something Else?
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