Polyethylene glycol

Author: Prof. Dr. med. Peter Altmeyer

Last updated on: 10.02.2022

Synonym(s)

Macrogol; Macrogole; PEG; Polyethylene glycol; Polyethylene glycols

Definition
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Polyethylene glycols (PEG; also macrogol as a drug), are chemically inert, water-soluble and non-toxic polymers of varying consistency (liquid or solid) depending on chain length, with the general molecular formula C2nH4n + 2On + 1, formed by polymerization of ethylene oxide. Depending on the chain length, PEGs have different properties. Polyethylene glycols with an average molecular mass between 200 and 400 Da are non-volatile liquids at room temperature. Higher molecular masses result in wax-like solid consistencies.

The most important property of all polyethylene glycols is their solubility in water, their long shelf life (they are not subject to the usual biodegradation processes) and their good general and especially good skin compatibility.

PEG(s) are called by different names depending on their molecular size:

Macrogols (INN): PEGs used as ointments (see macrogol ointment) as well as laxatives in medicine. They are neither absorbed by the skin nor broken down by the intestine. Their molecular weight is used to describe them in more detail; e.g. macrogol 400 = molecular weight of 380-420. PEGs in cosmetics correspond to macrogols in medicine. The term "macrogol 400" is synonymous with "PEG-9", a PEG consisting of 9 EO units.
PEG Beeswax: gel former in oleogels. The degree of ethoxylation is indicated with a hyphen after the PEG and can range from about 3 to 20.
PEG esters: are produced by the ethoxylation of carboxylic acids. Used e.g. in shampoos.
Polysorbates: These include e.g. surface-active substances such as Tween.
PPG: Polypropylene glycols are produced analogously to PEG from propylene oxide (PO). They are used as a substitute for mineral and vegetable oils.
Sodium Laureth Sulfate: Used mainly in shampoos and detergents.
Sodium Laureth Phosphate: Sodium Laureth-4 Phosphate is used in detergents and as an emulsifier in creams.
Higher molecular weight PEGs form moisture-retaining films on the skin surface, which have little effect on the skin barrier layers due to their lack of penetration.

Undesirable effects
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The allergological relevance of polyethylene glycols is considered to be very low.

In the case of topical application of macogols, it is of importance that only the low-molecular polyethylene glycols can penetrate the skin at all; they are therefore most likely to be of allergological relevance.Topical applications to skin and mucous membranes lead primarily to contact urticaria.

With systemic application (oral, intramuscular, intravenous), allergic reactions of the immediate type have been described in isolated cases. Besides palmoplatary pruritus, generalized urticaria and angioedema, severe, life-threatening anaphylactic reactions have also been described.

A complement factor C3-dependent complement activation is discussed, whereas already small amounts may lead to severe reactions. Furthermore, the induction of a specific IgE-mediated immune reaction (Hyry H et al. 2006) is suspected, although specific IgE has not yet been detected.

Diagnosis: In addition to history and clinic, positive reactions are frequently found in intradermal and prick tests.

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Incompatibility
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If a contact allergy is suspected, the block Hermal Cooling Lubricants I, ointment bases and emulsifiers (polyethylene glycol ointment); test concentration 100 % can be used.

Note(s)
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In addition to the pegylation of therapeutics, PEG is ubiquitously used in the manufacture of cosmetics, e.g. in perfumes, deodorants, insect repellents, lipsticks, toothpastes, hair care products). They are also used in foodstuffs, pharmaceutical preparations, liquid preparations (manufacture of injectables), ointment bases, suppositories, tablets and coated tablets.

PEGs, like the structurally similar diethyl ether (the substance usually referred to as "ether"), are sensitive to oxygen. In the presence of UV light they form highly reactive hydroperoxides, which were one of the causes of the so-called"Mallorca acne".

Polidocanol also belongs to the PEGs and is widely used as an anesthetic and antipruritic agent (see below Polidocanol lotion and cream) and as a sclerosing agent (aethoxysclerol). Polyethylene glycol is usually listed with a number in the list of ingredients (e.g. PEG-8 in ®).

Due to the wide range of applications, contact allergies may occur, although very rarely (see above).

Literature
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Borelli et al: Systemic immediate type reaction to macrogol 4000, Allergo J 14, 39 (2005).
Dewachter et al (2005) Anaphylaxis to macrogol 4000 after a parenteral corticosteroid injection. Allergy 60: 705-706
Hyry H et al.(2006) Two cases of anaphylaxis to macrogol 6000 after ingestion of drug tablets. Allergy 61:1021.
Quartier S et al. (2006) Allergic contact dermatitis to copolymers in cosmetics--case report and review of the literature. Contact Dermatitis 55:257-267. review.
Wolf G (2014) Polypragmasia in formulations. Dermatologist 64: 418-419