Hello,
Rash in the belly button area is usually due to infections chied ones being fungal infection. Most cases of fungal infections respond to over-the-counter products, which contain any of several basic ingredients: miconazole, tolnaftate, terbinafine,ketaconazole and clotrimazole.You can consult a pharmacist and get any cream or lotion containing these ingredients. Some of them are Lamisil, Monistat derm, Mycelex, and NizoralYou can also use selsun shampoo on these white patches.
If the symptoms persist then it will be best to get it evaluated from a dermatologist. Other possibilities have to be ruled out then. I suggest you a dermatologist’s examination to confirm the diagnosis.
I hope it helps. Take care and regards.