Planefag with chemistry experience here. What you are reacting to are either isothiozolinones, parabens or oxazolidines, all of which are used as preservatives in shampoos.
The most notorious of these was one called Kathon 886MW that found it's way onto the Red List for being such a rampant skin sensitiser.
Read the labels and check what preservatives are there. There's a LOT of bullshit talked on shampoo and cosmetic labels, such as Aqua (water), Parfum (odorant) and lots of fancy sounding names that only chemists can decipher.
If you aren't sure, post 'em up here and i'll do my best to help.