It could just be toddler diarrhoea Toddler's Diarrhoea, Loose Stools in Children | Patient.co.uk it's quite common and normal - DS2 had it and in hindsight, DD2 had it as well. With DS2 it was quite bad and we had him tested for coeliac disease and a few other things. He did have trigger foods though - no juice or cordial at all and anything with too much fibre in it were no-no's and we had to limit his fruit to one piece a day. He grew out of it at about 4.5yrs.