This hair thing is interesting!  A really new thought!  I have identical
twin boys, now aged 15.  The easiest way to tell them apart at birth (the
*only* way for the first few days until I got to know them better!) was
because Bryn had straight sticking-up hair, whereas Shaun's was smooth.
They were exclusively breastfed for over 7 months, and partially breastfed
for a looooong time. Neither of them have any allergies, but I have trusted
them to know what's good for them.  Bryn will not touch milk or eggs unless
these foods are *heavily* disguised, whereas Shaun loves both.   Maybe
there's something in this potential allergy thing after all.

Pamela Morrison IBCLC, Zimbabwe