welcome to healthcare magic forum
thank you for your query
yes ,ppd may remain in hair after few weeks of application
in sensitive skin period may be longer
alcohol make hair dry and rough .
you should apply good conditioner and oil in hair .
use only mild shampoo 2-3 times a day
for itching you can take cetrizine
once a day
avoid sun and wind exposure to hair
better to consult dermatologist
if not improved in few days
i hope i answered your query