B Sys 20mg Tablet belongs to a group of medicines known as antihistamines. It is used in the treatment of allergy symptoms such as runny nose, stuffy nose, sneezing, watery eyes, and congestion or stuffiness. B Sys 20mg Tablet can be taken one hour before or two hours after food, but take it at the same time to get the most benefit. It should be taken as your doctor's advice. The dose and how often you take it depend on what you are taking it for. Your doctor will decide how much you need to improve your symptoms. Remember, dosage is decided on the basis of the type of medicine (tablet or syrup ), age, and present medical condition of the person. You should take this medicine for as long as it is prescribed for you. If you do not observe any improvement in the symptoms, consult with the doctor.The most common side effects of this medicine include headaches and drowsiness. If these bother you or appear serious, let your doctor know. There may be ways of reducing or preventing them. Generally, it is advised to drink plenty of fluids while on treatment with this medicine. To overcome dizziness, avoid driving or attention-seeking activities until you know how the medicine affects you.Before taking this medicine, let your doctor know if you are pregnant or breastfeeding. Your doctor should also know about all other medicines you are taking as many of these may make this medicine less effective or change the way it works.  You must avoid fruit juice before taking the medicine.