Infants from anthroposophic families have low cortisol levels and low risk of IgE-sensitization during first 2 years of life. Our aim was to study the impact of an anthroposophic lifestyle and cortisol levels at 6 months on allergy sensitization up to age 5 years. A total of 507 families participated from maternal healthcare centers. Parental lifestyle was categorized as anthroposophic, partly anthroposophic, or non-anthroposophic. Blood samples for analyzes of sensitization were obtained from parents at inclusion and from children at 6, 12, 24, and 60 months. Salivary samples were collected at home at 6 months. Sensitization increased from 2.9% to 26.0% in the anthroposophic group, from 8.4% to 26.8% in the partly anthroposophic group, and from 19.1% to 44.1% in the non-anthroposophic group. Children from anthroposophic families had lower cortisol levels in the morning, afternoon, and evening. The odds ratio (OR) for anthroposophic lifestyle was always <1 and lowest at 12 months (OR, 0.10; 95% CI, 0.03-0.36). Adjusting for cortisol levels at 6 months increased these ORs at 12 and 24 months. At the same ages, ORs for sensitization were elevated also for cortisol levels at 6 months. Analyzes in children not sensitized at 6 months confirmed the cortisol-related risk of sensitization. Children from families with an anthroposophic lifestyle have lower risk than comparisons of developing sensitization up to 5 years. This risk is partially explained by low cortisol levels during infancy. High cortisol levels at 6 months predict sensitization up to 24 months.