Eczema, reflux, colic, diarrhoea and even constipation may be caused by an underlying milk allergy.

BBC: Children with allergies 'being let down'

Lewis' mother died from colic six weeks after he was born and his owners could not look after him.

BBC: Rescued Amersham pony mothers orphan foal in Norfolk

"You can talk to parents 25 years later and they'll remember it like it was yesterday, " says Barry Lester, director the Colic Clinic at Brown University's Center for the Study of Children at Risk in Providence, R.

WSJ: Is It Colic -- or Is It Acid? Pediatricians' New Rx

Indeed, months of crying and sleeplessness can take a huge toll on the family, whether it's due to reflux or colic or another cause.

WSJ: Is It Colic -- or Is It Acid? Pediatricians' New Rx