Localised pain in the anus after diarrhoea is considered to be possibly caused by increased bowel movements.
First of all, symptomatic treatment of diarrhoea should be actively carried out. You can choose to take oral montelukast or necessary antibiotics, and choose to wash the anal area with light salt water after defecation, and then, choose to apply an appropriate amount of erythromycin ointment to the anal area.