There are a few different reasons why you might develop a fungal infection in your head. One of the most common reasons is using dirty hair brushes or combs. The fungus can also grow on your scalp if you do not shampoo and condition your hair regularly. Exposure to moisture and humidity can also cause fungus to grow, as well as wearing tight hats or headbands. If you are experiencing any of the symptoms of a fungal infection, such as itchy scalp, redness, or dryness, consult a doctor for diagnosis and treatment.