The evacuant solution (ES) is a drug that has been used to clean the colon. The most common described side effects when using this drug are abdominal symptoms; skin rash is rare. We report on two patients who presented urticaria and angioedem after the intake of an evacuant solution to make a rectoscopy. We performed allergy studies: skin prick tests with common inhalants, pure ES and the components (polyethylene glycol 4000 (PEG 4000), KCI, NaCO3, NaPO3, NaSO3, NaCI, neohesperydine, potasic acesulfam and orange flavouring), intradermic test, total serum IgE and single-blind placebo oral challenge with ES and the components. We report on the first cases of immediate allergy reactions (type1) caused by oral intake of a drug containing PEG 4000 which were demonstrated by intradermic tests and oral challenge.