[smartbutdumb (OP)]

When we get bitten by an insect, flea or midgey etc...what causes the itch? Is it just the normal inflammatory response or something else?

[MayoFlyFarmer]

i know that with mosquitos (and I'm guessing with most other insects) when they bite you, they inject a bit of a numbing agent so that you are less likely to feel the bite (and thus less likely to swat them).  it is this numbing agent that we later have a minor allergic reaction to.