Background Psoriasis is a genetically determined systemic skin disease, although environmental trigger factors are required for disease manifestation. Some of these triggers, such as stress, infections and drug exposure, have been identified. Objectives To explore the role of early nutrition as a risk factor for the development of psoriasis. Methods Parents in the All Babies in Southeast Sweden (ABIS) prospective birth cohort (n = 16 415) answered questionnaires at birth and when their children were aged 1 and 3 years. A diagnosis of psoriasis was determined from the Swedish National Patient Register and National Drug Prescription Register. Statistical analyses were conducted using custom-written R scripts. Results Individuals breastfed for < 4 months and who received infant formula before 4 months of age had a higher risk of psoriasis [odds ratio (OR) 1.84 (P = 0.02) and OR 1.88 (P = 0.02), respectively]. At the 3-year follow-up, the increased consumption of fish, especially from the Baltic Sea, increased the risk of psoriasis (OR 9.61; P = 0.003). In addition, the risk of psoriasis increased following the consumption of a large volume of milk (OR 2.53; P = 0.04). Conclusions Our study underscores, for the first time, the impact of very early nutrition on the manifestation of psoriasis through early adulthood. Exclusive breastfeeding for 4 months appears to be protective.