Researchers found the risk of childhood asthma was reduced by almost two-thirds in babies fed oats before they reach five months of age compared to those introduced to them later.
The scientists also found babies fed fish early on had much lower rates of hay fever by the time they were five years old.
The findings, published in the British Journal of Nutrition, clash with Scottish government and European infant feeding guidelines, which recommend breast feeding for six months before introducing solid foods.
Carina Norris, a nutrition expert, said: "At this stage I would not want to go against the Department of Health guidelines.
"But new research is published all the time that turns previous knowledge on its head."
According to Asthma UK, Scotland has one of the highest rates of childhood asthma, with at least 72,000 suffers.
Porridge has enjoyed a popular revival in recent years, with suggestions that a medium-sized bowl each morning can reduce cholesterol by ten per cent.