What are PEGs?

PEGs, also known as macrogols, are compounds widely used in medicines, cosmetics and household 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.

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.

Symptoms can include:
  • right_arrow_orange_icon Nettle rash (also known as hives or urticaria)
  • right_arrow_orange_icon Swelling (also known as angioedema) which can affect any part of the body
  • right_arrow_orange_icon Difficulty breathing
  • right_arrow_orange_icon Severe wheezing
  • right_arrow_orange_icon Itchy eyes
  • right_arrow_orange_icon Runny nose
  • right_arrow_orange_icon Feeling faint or dizzy (due to sudden drop in blood pressure)

Diagnosing PEG allergy

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.

Some items that may contain PEGs:
  • right_arrow_orange_icon Laxatives such as Movicol
  • right_arrow_orange_icon Depot steroid injections
  • right_arrow_orange_icon Medicines, such as painkillers, antibiotics, antacids, suppositories
  • right_arrow_orange_icon Creams and lotions
  • right_arrow_orange_icon Hand soaps
  • right_arrow_orange_icon Shower gels
  • right_arrow_orange_icon Hair products (shampoos, conditioners, hair dyes)
  • right_arrow_orange_icon Dental products (toothpaste, mouthwash)
  • right_arrow_orange_icon 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 auto-injectors in case of emergency.

The Medicines and Healthcare products Regulatory Agency (MHRA) recommend that you have two adrenaline auto-injectors available at all times in case one is broken or misfires, or you need a second injection 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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