Cross-reactivity between propylene glycol and macrogol?
Is there any data in regard to cross-reactivity between propylene glycol and macrogols?
I asked Rachel Robison, MD for her input on your question. Her response is as follows:
"Propylene glycol (PG) and Macrogols (such as polyethylene glycols or PEGs) are synthetic substances that are used as vehicles in various cosmetic and medicinal products. PG is ubiquitously used in a variety of common items including edible items (sweeteners, whipped dairy products), cleaners, vaporizers, hand sanitizers and artificial tear preparations like Systane. It is a common cause of allergic contact dermatitis (ACD) and was named the ACD Society’s allergen of the year in 2018. In addition to causing contact dermatitis with cosmetic exposure, systemic contact dermatitis has been reported after oral ingestion. As PG is both a weak sensitizer and a cause of irritant dermatitis, patch testing interpretation can be difficult to interpret as testing results may not be robust if low concentrations are used and may lead to irritant response with higher concentrations. 1,2 There are no reports upon literature review of IgE-mediated or anaphylactic reactions to PG.
PEG is also found in multiple cosmetic and industrial products and is used quite frequently in medicine as it is found in PEGylated medications, hydrogels, tablets and lubricants. Though thought to be fairly safe, there are multiple reports of immediate type hypersensitivity reactions consistent with anaphylaxis. A 2016 systematic review, noted 37 case reports of PEG induced reactions, 80% due to oral PEG exposure.3 Some cross reactivity does appear to exist between PEG and structurally related polymers such as polysorbate 80 and poloaxmer.3
PG and PEG have dissimilar chemical structures. PG is a small, single molecule with 3 carbons and 2 OH groups ( ie a double alcohol). PEG is a multi-unit polymer with a differing molecular weight and backbone. Historically the types of reactions these agents cause are dissimilar as noted above. Few studies have looked at sensitization to both agents. A single Turkish study retrospectively looked a patch testing for both PG and PEG as a marker for nitrofurazone allergy.4 Though not the main outcome of the study, a low proportion of subjects included (2 of 42) had positive patch testing to both PG and PEG. Thus there is not sufficient literature to support cross reactivity between PG and PEG. Though I am not sure which agent your patient has reacted to in the past, given how ubiquitous both agents are it would be prudent to take a detailed history as it is likely they are already tolerating exposure to the other agent which can provide some reassurance."
1. McGowan MA, Scheman A, Jacob SE. Propylene Glycol in Contact Dermatitis: A Systematic Review. Dermatitis. 2018; 29(1):6-12.
2. Lalla SC, Nguyen H, Chaudry H et al. Patch testing to propylene glycol: The Mayo experience. Dermatitis. 2018; 29(4) 200-205.
3. Wewande E and Garvey LH. Immediate-type hypersensitivity to polyethylene glycols: a review. Clin Exp Allergy. 2016; 46(7): 907-922.
4. Ozkaya E and Kilic S. Polyethylene glycol as marker for nitrofurazone allergy: 20 years of experience from Turkey. Contact Dermatitis. 2018; 78(3): 211-215.
I hope this is helpful.
Daniel J. Jackson, MD, FAAAAI