Buying hair-care products at CVS or other drugstores may not get you the best bargain. In fact, they may be fueling a gray-market industry that sells counterfeit, stolen, or expired goods. This is known as diversion, and diverted products are typically more expensive and less effective than the bona fide product. Sources have even reported the presence of bacteria in diverted professional hair products.
To be safe, buy your hair products and professional shampoo at a salon. It may be at a higher price, but many salons' anti-diversion policies protect against the gray market so you'll know what you're buying is authentic.