The aim of the present prospective study is to investigate whether the consumption of certain probiotic strains over a six-month winter/spring season would be able to affect the incidence and duration of upper respiratory tract infections, in otherwise healthy children as well as determining whether a combination of two strains would perform differently from a single strain version.

Inclusion Criteria:

• Children aged 3-5 years of normal nutritional status and health

Exclusion Criteria:

• Contraindications to dairy products (lactose intolerance or cow's milk allergy)
• Indicators of inflammatory disease, intestinal disease, Crohn's disease, colitis, celiac disease
• Chronic cough from recurring respiratory distress-related diseases
• Hirschsprung's disease
• Cystic fibrosis
• Other metabolic, neurological, or anatomic alteration that predisposes participation
• Intake of probiotics within the last 3 weeks