When your belly button suddenly starts itching the itchy belly button can sometimes be caused by a fungal infection called Candida which is a yeast infection that grows in dark and damp areas of your body which can be your belly button.
The Candida or candidiasis can cause your belly button to itch and even cause a white discharge from your belly button.
You might also have a red rash in your belly button due to the fungal infection.
You can use some apple cider vinegar or fungal cream to help get rid of the fungal infection in your belly button.
Make sure to wash the belly button daily and use some fungal cream or fungal powder to help get rid of the fungal infection that is in your belly button.