Hi Dr Charles, My Baby Is Turning In To 6months

Hi Dr charles, my baby is turning in to 6months . He has a seasonal and dust elergy which will create flu in his nosel..which medicine u will recommend me and what formula milk is suitable for him..i am giving him enfamel A+ and gerber oatmeal does it ok? Aur i switch to anyother formula milk and cereal? Does nestle cerelac forming constipation or gas issue?