@burcinc-- Just because you have been using a product for some time doesn't mean that you can't be allergic to it all of the sudden. Sometimes, the immune system can weaken and things that didn't bother us before might.
This goes for shampoos, conditioners, hair products like hair spray, perfumes and lotions. Even laundry detergent can cause an allergic reaction that causes itching.
Another possibility is bed mites. But mites usually cause red, itchy skin and a rash.