What are the side effects of robitussin (guaifenesin) for cough & chest congestion?

Symptom control: Do not give these products to children younger than 4 years of age as they can cause problems. Guaifenesin is used to relieve chest congestion . Guaifenesin may help control symptoms but does not treat the cause of symptoms or speed recovery. Guaifenesin may cause side effects. Tell your doctor if any of these symptoms are severe or do not go away:headache, nausea, vomiting.