Hi Jeyanthi raj, You can wash your hair with Shikakai only once in a week. Taking plain head bath (with out using shikakai or shampoo etc)(just plain head bath) twice in a week is advisable. By this your scalp is prevented from any dryness mainly that itchy dandruff. In case you are not comfortable with twice a week head bath, you can take head bath alternate days. And also make sure that you wear a cap or scarf over your hair if you are stepping out the Sun. The Sun severely damages your healthy hair if not protected.
For lengthy and healthy hair your diet also very important.
Dates, Curry leaves chutney and greens should be taken with out fail. Soak fenugreek seeds in curd previous night and have it in empty stomach every day morning. This will get you Strong shiny hair. Vitamin B rich food items in your diet also important. All the best. thank you!