scalp and face itching from shampoo?

For a number of years (worse in the last 3) I have been having a reaction to what I think is my shampoo. My head breaks out in a rash and my forehead and sometimes my face also get red itchy splotches. These are not necessarily raised but are most likely some sort of urticaria. I have tried many brands of shampoos from cheap to expensive salon varieties, but eventually I will develop this reaction.
Sometimes the reaction is immediate, other times it will take 3 months of use to develop. It does not appear to be related to sodium laureth sulfate as I have reacted to shampoos with and without. I use Cetaphil soap, because I react with sensitive swollen hands to any other types of soap. I hope someone here will have some suggestions as to what I can use or what it is that I might be reacting to.

[National Jewish]

Most shampoos are composed of 10 to 30 ingredients and many of them have been reported to cause allergic reactions.  Your best bet would be to see a dermatologist who could recommend non-allergenic shampoos and/or conduct patch tests to the more common shampoo allergens/irritants.  Otherwise, you will be left guessing indefinitely.