Living BACTERIA, which, when given in sufficient dose to colonise the intestine, may produce a beneficial effect for the host. Many probiotics are LACTIC ACID bacteria – for example, LACTOBACILLUS or bifidobacterium. They may help some cases of travellers’ DIARRHOEA, reducing the period of acute symptoms – particularly if the infection is caused by one of the ROTAVIRUSES and may be of use in eczema in young children. Many other claims are made for their benefit but these are not backed up by research evidence.