If you have dandruf and itching you are lucky. You need an antifungal shampoo. See your doctor about antifungal treatment.
Alopecia areata (AA) is usually caused by something you are doing to your body. Although in a smaller percentage it is just natural. I estimate 60/40.
In my case stress is causing AA. I am investigating two reasons currently one is lack of sleep which I have since fixed. The other is a digestive disorder from stress induced over eating which causes digestive symptoms like hemeroids or colitus in my body.
Ask yourself what has changed in my diet or my behavior around the same time as AA. In talking to many people with it that recover it seems to be nearly always related to sleep, drinking alcohol, diet, or exercise. Which all happen to be related.
For me it was a change in my stools that I noticed around the same time as AA.