Hair regrowth shampoo is just one part of any program for fighting or reversing hair loss. Though the ingredients may differ, in general the shampoos in these systems do one or two main things. They are designed to clear away dead skin cells and get rid of excess scalp oils that may be clogging follicles. Some hair regrowth shampoo formulas use ingredients that are believed or proven to reduce the amount of DHT on the scalp. High DHT levels are the primary cause of hair loss.

Shampoos with DHT blockers claim to produce new hair growth in a period of two to three months. Many people combine shampoos containing ingredients that block DHT with a topical treatment such as minoxidil in an effort to maximize the benefits to the hair and follicles.
Quite often, special shampoos are sold alongside topical hair loss preparations, and in systems that include nutritional supplements designed to slow hair growth and maximize the health of existing hair. While the shampoos themselves, with the exception of Nizoral, which will be mentioned later, don't have medical effects, they are designed to maximize the utility of the topical treatments while keeping existing hair healthy.
One of the most popular types of shampoos used in hair regrowth systems is Nioxin. There are actually several variations on Nioxin, formulated for different hair types: coarse, fine, normal, or thinning. Many people who are not losing their hair like Nioxin shampoos and use them anyway for the way they make their hair feel.
Progaine Volumizing Shampoo is made by the manufacturer of topical hair loss treatment Rogaine, which contains minoxidil. Progaine shampoo doesn't contain minoxidil, but is designed to gently remove build up of scalp flakes and styling product build-up that can weigh hair down and cause it to look thinner and flatter. 

DS Laboratories Revita is a special thickening shampoo that does not contain sodium lauryl sulfate or sodium laureth sulfate, which some people find irritating and drying. Revita contains caffeine, copper peptides, emu oil, biotin, and other components. It is designed to have antioxidant effects and anti-DHT properties.

Nizoral is actually a dandruff shampoo that contains an anti-fungal ingredient called ketoconazole that is designed to stop dandruff. However, anecdotal evidence is leading scientists to study whether this ingredient actually works in a manner similar to minoxidil. Though there is no definitive proof yet, many men using minoxidil also use Nizoral in an effort to attack baldness in two ways.