Hello, Doxycycline is a very good antibiotic for tick bite prophylaxis and as any antibiotic with a wide spectrum has a risk of killing the normal bowel flora and causing problems with the bowel.Taking yogurt is helpful but you can also take the probiotics separately daily to help reduce this. Try to avoid very sweet food and fatty food as these may be difficult to digest and may cause gas in the process. Try to avoid milk during the treatment, yogurt and cheese are ok. If you notice diarrhea, abdominal pains and or blood with stools you will need to let your doctor know as soon as possible. I hope I have answered to your query. Let me know if I can assist you further. Take care Regards, Antoneta Zotaj, General & Family Physician