Hi there Smita.
I am afraid that in your current situation, it would be hazardous to attempt another hair dye adventure.
You may use 'Natural Mehendi' if you are determined to use something. Be careful not to use "khali-Mehendi" as this black substance also contains dyes.
It appears a reasonable assumption that you have developed an
allergy to dye components judging by the type of
hair fall that you describe following the use of the hair color.
For the grey hair & to enhance/boost your hair in the interim, might I suggest you try any 2%
Minoxidil lotion (MX lotion) applied on dry
scalp twice daily. In addition, the use of Altris gel (Melitane component) may help 'limit' the spread of the white hair.
If in Bangalore, please drop into Vikram hospital for a more in-depth analysis.
Good Luck & Wish you continued good heath & healthy hair!
Dr Praveen Rodrigues MD