Hi, Becelac PB is generally considered safe. It is actually a probiotic which consists of of live beneficial bacteria that naturally live in your body. It is commonly prescribed to treat diarrhea, constipation. inflammatory bowel disease, irritable bowel syndrome, fungal infections, urinary tract infections, gum disease, lactose intolerance, and eczema. It is not used for the treatment of headache. For the treatment of headache its causes should be determined first and treated accordingly by your doctor. Becelac PB is well tolerated by most of our patients however it can cause a temporary increase in gas, bloating, constipation and thirst. Although it is quite rare however, it may increase the risk of infection, resistance to antibiotics, develop harmful products from the probiotic. The risk may increase if you have a medical condition that weakens your immune system, have recently had surgery or have other serious medical conditions. Take care. Hope I have answered your question. Let me know if I can assist you further. Regards, Dr. Mohammed Taher Ali, General & Family Physician