Alopecia is a blanket term for hair loss of any kind. There are many types and causes of hair loss (alopecia), most of which can be effectively treated. Hair loss may be genetically inherited, or it may be caused by a variety of other factors including protein or other dietary deficiency, hormonal imbalance, and stress. Hair loss can also be the first sign of an otherwise undiagnosed or undetected underlying illness.
The main type of hair loss for which there is no effective treatment is genetically inherited hair loss (known as Male Pattern Baldness or Androgentic Alopecia).
It is important to note, however, that this condition can and does affect females too, even though it is called Male Pattern Baldness (it is gene-linked, not sex-linked). In women, it is likely to lead to diffuse hair loss, (a general thinning of the hair density) rather than to obvious bald patches.
Although there is no cure for this condition, hair loss can be limited or slowed down in some cases and treatments are likely to be more effective on women than on men.
The important thing to understand is that the best that can be said of treatments for genetically inherited hair loss is that they can be effective to some degree on some people some of the time.
Can occur after infectious scalp disorders or, more rarely, they are auto-immune conditions (when the body attacks the hair follicle as it would invading bacteria).
Other types of alopecia that you may have heard of include Alopecia Areata, Alopecia Total is, Alopecia Universalis and Traction Alopecia (there are others, too). These are all entirely distinct from Androgentic Alopecia (above) and have a much better chance of responding to professional diagnosis and treatment.