Hi & Welcome. Ofloxacin + Ornidazole combined formulation of antibiotics is generally prescribed for the susceptible bacterial and protozoal infections including diarrhea. Allergic reaction in this combination is usually due to one antibiotic either Ofloxacin or Ornidazole. So, first the exact causative antibiotic responsible for the allergic reaction should be identified and should not be used in future. Since you are allergic to this combination of antibiotics you can use antibiotics like Doxycycline or Amoxycillin after consulting your doctor. However, a culture and sensitivity of the stool is recommended to choose the most appropriate antibiotic in your case. Hope this answers your query.