It's mostly alopecia aereata. It's sudden patchy loss of hair over scalp. Mostly due to autoimmune cause. Associated with other autoimmune disease. But need to ask you some questions to rule out infection, with clear pictures.
It's reversible with proper prescription medicine.
Next Steps
consult or chat with me online/any Dermatologist for treatment
Health Tips
general hair care: use shampoo regularly and dry your hair in sunlight after bath. Do not rub your hair while washing/drying hair.
Do not apply oil immediately after taking bath.