In my practice I require a referral from an allied health professional for any diagnosed condition, including diagnosed alcoholism...
That being said, while there is a physiological component to it, all behaviors have underlying emotions, beliefs, initial sensitizing events and interpersonal relationships which can be addressed effectively in the hypnotic state. And quite honestly the mind has great power over the physical body and so symptoms of detoxification/withdrawal can also be supported with hypnotherapy. Think of it this way, if we can use hypnosis to numb the entire body for invasive surgery (we can) then we can abate symptoms of withdrawal for as long as needed.
Alcohol may be the outward expression or behavior but what are at the core of any unwanted behavior are underlying beliefs and relationships with unmet needs. In my practice I work to resolve these underlying causes so that the behavior becomes unnecessary from the new place of positive beliefs. So in short, yes hypnotherapy utilized properly can help resolve alcohol addition (or any other addiction)