What dangers are there in feeding baby "adult" oatmeal all mashed up? - danger is my bag baby

The recipe in the book Super Baby Food suggests mixing normal "adult" in powdered oatmeal and oat flakes used to make baby. I am a little over 2 months. But I realized that the bag of oatmeal, oat says that will be processed on machinery that also processes nuts and food allergens. Now I have my baby food allergens exposed to most often? Is the risk of allergies than before? If so, must now turn to commercial baby or "damage" oatmeal done already?