What makes us fear something?

Fear is a funny thing.. why do we fear things?

I believe it is to do with our subconcious where we remember what went wrong in the past and how it affected us thus not wanting to go near the associated 'fear' anymore. For example in the past when I was a little girl  I went to Butlins and one night I ate a hotdog followed by crisps followed by popcorn. That night I was sick (unsuprisingly) and for years after that I didn't touch popcorn. I find it odd how I blamed popcorn and not the other food items, but it did affect me for quite a long time. I didn't fear it exactly but I didn't want to risk eating it in case the same thing happens as I guess I kinda fear being sick. So that's where it all links up! It's the same with other food i've had in the past such as a Subway when I was ill in 2006 (not touched it since) and a KFC that was left so long it clearly wasn't right and made me ill (not touched a KFC since 2007). However I am going to try KFC again one day soon as it did used to taste so good when it was cooked right..

My other fears are of the unknown - dying and I really don't like people in masks for some reason. Can't quite figure out the mask fear but I guess maybe that's too linked to the unknown. It's funny how if you think about it everything links neatly together.

What fears do you have and why? Comments welcome.