Can piggybacks cause hairgrowth?
Do "piggy-backs" cause hair growth?
Not usually! I enjoyed this article which showed piggyback can cause hair growth if you are 9 months old & grandpa is using minoxidil (Rogaine).
Reference
Farsani et al. Piggyback acquired hypertrichosis. Pediatr Dermatol 2014. 31(4):520
This article was written by Dr. Jeff Donovan, a Canadian and US board certified dermatologist specializing exclusively in hair loss.