Allergy is the most common chronic disease in Europe and about 40% of the population suffers from it. The microbiota is closely linked to the immune system, being some probiotics characterized as beneficial contributing to reduce allergenic symptomatology. To ensure the predominance of beneficial
probiotics on the gut microbiota, the use of prebiotics is very important. Among the most important prebiotics are those of marine origin, standing out the fucoidan, a polysaccharide from brown algae (Phaeophyta). The effect of fucoidan on Lactobacillus reuteri in vitro growth behaviour has been studied,
using turbidimetry, plate count and statistical analysis. The fucoidan revealed a significant prebiotic effect increasing L. reuteri growth (≈ 2 log₁₀ cycles after 48 h exposure). The combination of the prebiotic effect of the fucoidan together with the direct action that it exerts on allergy and other health problems, make this molecule a promising nutraceutical for future.