My niece is 7 months old, and has long hair: around say 20-25cm. We are planning to cut her hair against our wishes because we think it could make it easier for her to catch a cough or cold. Is long hair seriously dangerous?
My youngest has only had one trip to get rid of some split ends - she is nearly 6, so her hair is long enough to sit on.
She had no problems with long hair.
Admittedly, during hot months we would tie it up into a pony tail, but that was just to help keep her cool and to stop her hair getting sweaty and tangled.
Have a look at the answers on this question about cutting a 15 month old's hair - I think they will be relevant for you.