Opioid Allergy or Something Else?

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.