What are PEGs?
PEGs, also known as polyethylene glycols are petroleum-derived polymers used in many medicines and products. They have many different uses, for example, as the surface coatings of tablets (medicines), ointment bases in creams, and as the active ingredient in some laxatives and bowel preparations.
Different types of PEG exist with different molecular weights. Research suggests allergic reactions are more serious with higher doses and with higher molecular weight PEGs.
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How common is PEG allergy?
PEG allergy is very rare, despite PEGs being widely used. However, there are some reports of immediate serious allergic reactions to PEGs (including anaphylaxis) in the medical literature. Some studies have described allergic reactions to PEGs caused by pharmaceutical drugs, such as laxatives and depot-steroid injections. PEG allergy can involve immediate reactions due to IgE-mediated responses.
Could I have a PEG allergy? What are the symptoms of PEG allergy?
Your doctor may suspect you have a PEG allergy if you have serious allergic reactions that start immediately after taking pharmaceutical drugs where the cause of the reaction is unconfirmed. Or, if you have repeated immediate serious allergic reactions to several drugs which are unrelated, or other products containing PEG.
Reactions to PEG usually come on quickly and are serious – most people experience anaphylaxis.
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a red raised itchy rash (known as hives or urticaria) anywhere on the body -
swelling of the face, lips and/or eyes
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a tingling or itchy feeling in the mouth
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mild throat tightness
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stomach pain, vomiting or diarrhoea
More serious symptoms of PEG allergy
The term for this more serious reaction is “anaphylaxis” (pronounced ana-fil-ax-is).
Most healthcare professionals consider an allergic reaction to be anaphylaxis when it involves difficulty breathing or affects the heart rhythm or blood pressure. Any one or more of the ABC symptoms above may be present.
In extreme cases there could be a dramatic fall in blood pressure. The person may become weak and floppy and may have a sense of something terrible happening. Any of the ABC symptoms may lead to collapse and loss of consciousness and, on rare occasions, can be fatal.
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AIRWAY – swelling in the throat, tongue or upper airways, hoarse voice, difficulty swallowing
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BREATHING – sudden onset wheezing, breathing difficulty, noisy breathing, persistent cough
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CIRCULATION – dizziness, feeling faint, sudden sleepiness, confusion, pale clammy skin, loss of consciousness or collapse
Diagnosing PEG allergy
Diagnosis may require specialist testing including PEG skin tests. People with confirmed PEG allergy have usually had repeated immediate serious allergic reactions before they had a diagnosis. Typically, they will have had reactions to several classes of drugs such as laxatives, injected corticosteroids, or antacids, all containing PEG.
The following do NOT mean you are at risk of PEG allergy
- A history of allergic reactions to foods and non-covid vaccines
- A drug allergy that has been confirmed or always happens after taking the same type of medication
- Chronic (long term) nettle rash or swelling
Avoiding PEGs
If you have a confirmed PEG allergy, your allergy specialist will advise you on which products to avoid. Always check medicine and cosmetic labels carefully for PEGs or macrogols. Some medicines will list all ingredients on the outer packaging along with the active ingredients. Others will list the ingredients only in the patient information leaflet (section 6.1 of the leaflet) inside the medicine box.
If you have a confirmed PEG allergy, always tell your healthcare providers, including doctors, nurses, pharmacists, anaesthetists and dentists, as well as your hairdresser.
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Laxatives such as Movicol
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Depot steroid injections
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Medicines, such as painkillers, antibiotics, antacids, suppositories
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Creams and lotions
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Hand soaps
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Shower gels
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Hair products (shampoos, conditioners, hair dyes)
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Dental products (toothpaste, mouthwash)
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Bone cements
Treatment for PEG allergy
If you have a confirmed PEG allergy, you should be given written drug notification from the allergy clinic and you should wear a medical-alert bracelet or pendant. As PEG is not always easy to avoid, you should be prescribed adrenaline in case of emergency.
The Medicines and Healthcare products Regulatory Agency (MHRA) recommend that you have two adrenaline devices available at all times in case one is broken or misfires, or you need a second dose before emergency help arrives.
Covid-19 vaccinations
The Pfizer and Moderna mRNA-based covid-19 vaccines both contain PEG. The Green Book (which provides the latest information on vaccines and vaccination procedures in the UK) says people with PEG allergy should seek the advice of an allergy specialist before having a covid-19 vaccination. If the decision is made to give an mRNA vaccine, this should be done in a hospital under medical supervision.
It is not known whether PEG allergy is the major cause of anaphylaxis to the mRNA-based covid vaccines. In the medical literature, there is one case of confirmed PEG allergy to the Pfizer vaccine in a patient with a history of anaphylaxis. The study also investigated three other cases with reactions suspected to be anaphylaxis, where PEG solution skin tests were negative.
Another study reported negative PEG skin tests in eight patients with a history of hypersensitivity to the Pfizer and Moderna vaccines and successful administration of the second dose of the same vaccine.
Key messages
- PEG allergy is very rare but see your GP if you suspect it
- Most people with PEG allergy will have a history of immediate serious allergic reactions to several different unrelated classes of drugs
- There is a small risk of anaphylaxis with any vaccine. It is not known whether PEG allergy is the major cause of anaphylaxis to the mRNA-based covid vaccines
- PEG allergy diagnosis can be challenging. The hope is that increased awareness of PEG allergy and improved access to PEG allergy testing will lead to earlier diagnosis and reduce the risk of being exposed to PEGs.
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