Hello dear, Thank you for your contact to health care magic. I read and understand your concern. I am Dr Arun Tank answering your concern. Mostly a white thing in anus of the baby is a fungal infection. But you can confirm the infection with the Grams staining, it will give us the Grams positive yeast cells. Prolong napkin can cause such infection. So avoid using the sanitory napkins for the baby for long time. If it s the fungal infection then taking the antifungal drugs can cure the infection, fluconazole oral suspension or in better part topical application of the fluconazole is the final treatment. Doctors supervision is necessary in this case. Please maintian good local hygiene this will help cure the infection at earliest. Please test the babies blood sugar and HIV status. Unknowingly many babaies my have this issues and so they are infected. Keep the baby open for some times this can make it dry and this dry ness cause fungus to die. I will be happy to answer your further concern on bit.ly/DrArun. Thank you, Dr Arun Tank Infectious diseases specialist, HCM.