Hello, Anorexia nervosa is a condition wherein the person restricts his diet fearing weight gain and maintains his body weight less than 85% of the expected weight. Now with that less appetite body doesnt get adequate nutrition and hence the immunity of the body goes down. This low immunity is further lowered by the increased amount of cortisol in the body of the anorexia patients. Dandruff is a condition which precipitates by reduced immunity and improper diet as well. Taking proper nutrition and proper treatment and care of hair will surely help in getting rid of the problem. There are many medicated anti dandruff shampoos available in the market and they are almost similar in efficacy. However the problem of dandruffis is just the tip of the iceberg. The major problem you should be concerned about is the Anorexia Nervosa itself. I am sure the psychiatrist who has diagnosed your case might have also started you on proper treatment for the same including psychodynamic psychotherapy. Cyproheptadine will increase your desire for the food. Amitrptilline and Fluoxetine are good drugs for Anorexia Nervosa. You should take atleast 500 kCal in excess of what your body weight requires which comes out to around 1500 KCal/day roughly. If you are not comfortable with solids, may be you can start with liquids initially. Hope I am able to solve your concerns. Thanks and have a nice day!