Rogaine was the first medicinal product in history approved by a major national health supervisory authority - the FDA (the US Food and Drug Administration) to treat male pattern baldness. To this day it is the only clinically-proven, topical method of treating hereditary hair loss that can be used by both men and women. Minoxidil is the sole active ingredient of Rogaine. The men's formulae contain 2% and 5% of minoxidil, whereas women's Rogaine only contains 2%.
Minoxidil is no longer patent-protected and, therefore, there are many producers of generic minoxidil (generic Rogaine) out there. Some of them offer plain Rogaine-like minoxidil but many others use minoxidil as a basis in their own hair loss formulas. The main difference between the plain, generic minoxidil and Rogaine is the patient's tolerance of the product, which largely depends on the type of solvents used in the formula. This topic has been discussed in more detail in the post "Rogaine, Regaine or Minoxidil".
The potential negative side effects of Rogaine, apart from itchy scalp and flaking, include conditions such as increased hair growth on other parts of the body, allergic reactions, very low blood pressure, irregular or fast heart beat, blurred vision, swelling or puffiness of hands, face and ankles, etc. If any of these conditions occur, treatment must be discontinued. Rogaine seems to fall victim of its own popularity and many consumer reviews reflect that. They seem to be worse than the reviews of numerous unproven, hair loss treatments. Rogaine often seems to be the target of bashing due to its negative side effects, which are being overemphasized in false testimonials posted by the snake oil marketers.