In very rare cases heart-burn, nausea, vomiting or diarrhea may occur. Rarely, the appearance of stomatitis, headache and tinnitus was reported.
According to single reports, allergic reactions were observed after the acetylcysteine application e.g. unloads, pruritus, exanthema, rash, swelling of the oro-pharyngeal mucous membranes, bronchospasms, tachycardia and a decrease of the blood pressure. The individually reported cases of bronchospasms were mostly found in patients having a hyper-reacting bronchial system in connection with asthma bronchiale, so-called "hyper-responders" (increased bronchial sensitivity to different stimuli).