Why do we need a blood test for PEG anaphylaxis?
Polyethylene glycol (PEG) is a commonly used ingredient in daily life and in a wide range of medications and medical devices. While safe for the vast majority of people, PEG has been increasingly recognized as a hidden trigger of rare but life-threatening allergic reactions, including anaphylaxis. What makes PEG-induced reactions particularly dangerous is their potential to occur without prior warning—even on first exposure—because most individuals have already been sensitized through prior, unnoticed contact with PEG-containing products.
In some sensitized individuals, the immune system produces PEG IgE antibodies, which can bind to PEG and trigger the rapid release of allergic mediators like histamine from mast cells and basophils. These events can lead to serious symptoms, ranging from hives and airway constriction to full-blown anaphylaxis. A blood test that detects PEG-specific IgE is a critical diagnostic tool—it allows clinicians to identify patients at risk before a reaction occurs. This is especially important for people who are candidates for high-dose or intravenous PEG-containing drugs, such as Omontys®, which was withdrawn from the market after multiple fatal anaphylaxis cases.
As PEG use expands in modern medicine, especially in advanced drug delivery systems and PEGylated therapeutics, a reliable and sensitive diagnostic test becomes essential for preventive care. Notably, newer immunoassay platforms like FocalTuning™ offer improved accuracy over older methods, reducing false negatives and better identifying at-risk patients. A blood test for PEG IgE not only improves patient safety—it also helps clarify the cause of unexplained allergic events, supports precision medicine, and informs safer drug development. In short, a better assay draws us closer to truth—and protects lives in the process.
Who should get the blood test of PEG IgE?
If you’ve ever had an unexplained immediate severe allergy or anaphylaxis, you may benefit from a blood test that checks for PEG-specific IgE antibodies. Polyethylene glycol (PEG) is a common but often overlooked ingredient in many medical products, and in rare cases, it can trigger serious allergic reactions—even without prior warning. For individuals preparing to receive PEG-containing treatments, such as mRNA vaccines or PEGylated biologics, this test offers valuable insight before exposure occurs.
This test is also an excellent alternative for people who can’t—or don’t want to—undergo traditional allergy skin testing. Skin prick tests can be uncomfortable, anxiety-inducing, and potentially risky for individuals with severe allergic histories. In contrast, this blood test is simple, low-risk, and non-invasive. A quick blood draw provides lab-based results without the stress, itching, or fear of a flare-up—making it ideal for anyone who needs clarity but wants to avoid the discomfort of skin-based procedures.
While PEG allergies remain rare in the general population (estimated at ~0.1%), the stakes are much higher in certain situations. People receiving high-dose or high–molecular weight PEG drugs (like Omontys®), those being treated via injection or infusion, and anyone with a history of unexplained anaphylaxis fall into higher-risk categories. For these individuals, preemptive screening using advanced platforms like FocalTuning™ can offer peace of mind and potentially life-saving information. As PEG use grows in medicine, identifying who’s truly at risk—through safe, accurate testing—will become increasingly important.
Can the blood test be used as a general screening tool?
In certain cases, yes. While PEG allergies are rare, the test can be valuable for high-risk groups—such as those entering clinical trials, people with complex allergy histories, or patients receiving PEG-containing treatments. It’s not something everyone needs routinely, but for the right individuals, it offers meaningful peace of mind.
Is there a risk of false positives or negatives?
As with any medical test, no result is 100% perfect. False positives may create unnecessary concern, while false negatives could provide false reassurance. However, newer versions of this test—especially those using flow cytometry—are showing high sensitivity and specificity. The key is to have your results interpreted by a qualified allergy specialist in the context of your personal history.
It has been noted of the frequency of immunization stress-related responses (ISRR)—psychogenic reactions that mimic anaphylaxis but are not immune-mediated. These ISRR cases commonly lacked anti-PEG IgE and did not exhibit biomarkers consistent with Type I hypersensitivity.
How can I know my medication contains PEG?
For those unsure whether their medication contains PEG, visit DailyMed at https://dailymed.nlm.nih.gov/dailymed/. Simply enter the drug name and check the “Ingredients and Appearance” section.