thanks for contacting HMC,
see many drugs are in homeapthy which can cure allerrgy to lactose like SILICEA, ANTIMONIUM CRUDUM,ARGENTUM NITRICUM and many more but that can be taken under care of classical homeoapath,
i would suggest you to go with homeopathy
for this complain and your baby will defenately get rid of this complain.
believe me in children homeopathy works much faster.