Hi thanks for contacting HCM... As you have hot weather there , excess sweating and friction at that site can cause boil that is by gram positive bacterial infection like staphylococci and streptococci... Take amoxyclav antibiotic for it.... Keep that area clean to prevent reccurence... Loose cotton cloths good for preventing it .. If boil increasing in size then incision and drainage necessary with regular dressing ... Avoid straining at stool... More water taken and fruits more.... Avoid excess spicy food as you have boil over rectal area... Take care. Dr.Parth