DD's almost 9 months old and has been eating a ...

DD's almost 9 months old and has been eating a wide range of solids since she was just shy of 6 months. So far i've not given her any of the most commonly known allergy-prone foods, although as far as i know neither DP's or my family's have any food allergies. So my question is what age did you start your child on these foods and how did you go about it? (I'm mainly interested in the big 4; egg, cows milk, nuts, fish.) TIA :)