Related Experiment Video
Updated: Jun 22, 2026

Production of Near-Infrared Sensitive, Core-Shell Vaccine Delivery Platform
Published on: October 20, 2020
Study of Excipients in Delayed Skin Reactions to mRNA Vaccines: Positive Delayed Intradermal Reactions to
David Pesqué1, Ramon Maria Pujol1, Orianna Marcantonio1
1Department of Dermatology, Hospital del Mar-Institut d'Investigacions Mèdiques, Universitat Autònoma de Barcelona (UAB) and University Pompeu Fabra (UPF), 08003 Barcelona, Spain.
Background:
Skin local reactions to mRNA COVID-19 vaccines have been linked to the use of vaccine excipients. The aim of the study is to evaluate the role of skin testing excipients in delayed skin reactions due to mRNA COVID-19 vaccines.
Methods:
Skin testing among a group of healthcare workers with skin reactions due to mRNA vaccines was performed. Patch testing and intradermal testing (IDT) with polyethylene glycol (PEG)-400, PEG-2000, trometamol, and 1,2-dimyristoyl-sn-glycero-3-phosphocholine were performed. Healthcare workers without skin reactions to vaccines were used for skin testing as controls.
Results:
Thirty-one healthcare workers (from a total of 4315 vaccinated healthcare workers) experienced cutaneous adverse vaccine reactions. Skin testing was performed in sixteen of the healthcare workers (11 delayed large local reactions (DLLR) and 5 widespread reactions). Positive IDT for PEG-2000 1% in DLLR was seen in 10 (90.9%) patients, in comparison with one (16.6%) individual with a delayed widespread reaction. Delayed positive IDT reactions for PEG-2000 1% on day 2 were observed in three (27.3%) patients with DLLR. Patch testing of the excipients was negative. Among 10 controls, only one exhibited a transient positive IDT reaction to PEG-2000 1%.
Conclusions:
Immediate and delayed reactions to IDT are frequently detected in patients with DLLR. The observation of positive delayed intradermal reactions to PEG disclosed only in patients with DLLR reinforces a possible role of PEG in the development of these reactions. Skin testing of other excipients is of little importance in clinical practice.
Related Concept Videos
Vaccinations
Allergic Drug Reactions
Site-Targeted Drug Delivery Systems: Polymeric Carriers
Drug Toxicity: Allergic Reactions
Hypersensitivity Reactions: Delayed Hypersensitivity Reactions
Vaccines

