Rabeprazole may cause the following side effects: headache, upset stomach, diarrhoea, stomach pain, vomiting, constipation, dry mouth, increased or decreased appetite, muscle or bone pain, drowsiness, dizziness, difficulty in falling asleep or staying asleep. Rarely, it may cause the following skin changes: rash, itching, sweating, urticaria (hives), alopecia (hair loss)- but all these side effects are an exception rather than a rule. Also please check if you are taking any other medications concomitantly.