<p>Like all medicines, Acetylcysteine can cause side effects, although not everybody gets them. In very rare cases, severe immune reactions may occur such as anaphylactic shock and severe skin reaction. In rare cases the oral administration can be followed by shortness of breath, upset stomach and bronchospasm. The most frequent side effects are headache, increased heart rate, stomatitis, pruritus, urticaria, nausea, vomiting, abdominal pain, fever, decrease in the blood pressure, diarrhoea and noises in the ears.</p>