1) too much milk. 2) bacteria infection See your Doctor. To respond to ur post( cant find it at d moment) abt building ur baby's immunity, 1)pls gv wellbaby multivitamin AND vitamin C drops daily. 2)If your baby is on complementary feeding,ur hygiene has to be top notch. 3) also offer fermented foods like pap. Yoghurt when much older say frm 12months.