welcome to the healthcaremagic community,
and hairfall is a vicious cycle, until u clear both u cant get rid of either. your hairfall could be hereditary or due to dietary errors.
coming to ur query of shampoo for dandruff, advise u to use a mild anti-dandruff shampoo like dove. (i m not promoting dove , but it is the mildest i know). but what u need to remember is u cant get rid of dandruff by just using the anti-dandruff agent once. for this u will have to use the anti-dandruff shampoo forever that's y i said use a mild one. second thing is the method of using an anti-dandruff shampoo. generally people apply the shampoo and wash off. but an anti-dandruff shampoo needs minimum of 20 minutes to work on and kill the dandruff :) so method is to apply the shampoo on ur scalp
like an oil then massage
the shampoo lightly on ur scalp and keep it for 20 minutes. then wash it off with water. ur dandruff will be visibly reduced in just one wash(irrespective of which shampoo u use) while doing so u might experience mild itching on ur scalp but that's normal.
now that U WILL GET DANDRUFF FREE IN THREE OR FOUR WASHES, does not mean u will stop using the shampoo, dear continue using it every-time u wash hair. advisable to wash hair atleast every 3rd day :)
and for your hairfall, suggest u the homoeopathic medicine weisbanden 200 two times a day for a week .
regarding ur query using SBL's arnica shampoo, my experience says never use herbals shampoos for dandruff scalp, it aggravates sometimes. instead u can use jaborandi oil of SBL.
hope this clears ur query.
Please accept my answer in case there are no further queries.
Good luck, take care,
Dr. Rooma Ramnani (email@example.com)