Probiotics in the treatment and prevention of allergy in children

Several fold increase in allergic diseases in developed, high-income countries during recent decades is attributed to environmental changes such as urbanization with improved hygiene. This, together with conquering severe bacterial infections during childhood, has reduced the microbial stimulation of the developing immune system of infants. Studies on the pathogenesis of allergy both in man and experimental animal have shown the importance of commensal bacteria in the gastrointestinal tract in stimulating and directing the immune system. The interest in modulating commensal bacterial flora with probiotics to prevent and treat allergy has multiplied in recent years.In the present review we report results on randomized, controlled studies in which childhood atopic eczema was treated or which aimed to prevent development of allergy during childhood.Nine studies with 639 patients have looked at the effect of probiotics in treatment of eczema. While 3 studied showed no effect, other studies suggested a moderate benefit of the use of probiotics on the severity of eczema. Studies suggested that the effect may be seen particularly in patients with food allergy and/or sensitization.Nine studies have reported on the prevention of allergy on 6 study population with altogether 1989 high risk infants. While the early study reporting the development of allergy at ages 2, 4 and 7 years showed a marked reduction of eczema in 77 treated infants, later studies have failed to show similar success. Two studies showed no effect. In the largest study with more than 900 children at age 2 atopic eczema was reduced by 20%, but at age 5 positive effect was present in only the subgroup of children who had born by cesarean section. None of studies has reported adverse effects of probiotics in infants.Result in both treatment and prevention studies are quite variable, the major reason being the use of different strains of probiotic bacteria and varying types of intervention. Even if the results are encouraging, we need a stronger effect. This may be reached by finding new strains of probiotics affecting stronger stimulation of immune system, together with longer lasting and varying treatment schedules. However, safety issues have to be observed.