Reactions to peroral propylene glycol

A peroral challenge test with 2--15 ml of propylene glycol (PG) was made in 38 patients with allergic-type epicutaneous test reactions to PG. Eight of 10 patients with a positive epicutaneous reaction to 2 % PG and seven of the other 28 patients with a positive epicutaneous reaction to 100-100 % PG developed an exanthem 3--16 h after ingestion of the drug. In all but one case the rash disappeared within 24--48 h without any medication. In one case the exanthem was treated with prednisone for 4 days, and the symptoms disappeared gradually in 6 days. None of the 20 control patients had skin symptoms. Nausea, vertigo and a curious sensation were recorded in four PG-sensitive patients and in three control patients. These symptoms were apparently due to the general pharmacodynamic effects of PG and they were regarded as non-allergic in nature. It was concluded that PG is a potential allergen and it must be added to the list of causes of drug exanthems.