Baby is too small to complain on its own. During such cases, following symptoms should be checked for, as this are the common symptoms seen when the baby is ill. They are: (a) Increase in the body temperature. (b) Constant crying. (c) Watering of the eyes. (d) Not eating food. (e) Vomiting and diarrhoea. Sickness is a condition used to refer to physical illness or disease.