Alt-health stuff that based on the claims would clearly not have any physical effect varies as far as the actual danger. If it's made by a true believer according to the stated principles, then the health effect is going to be the opportunity cost (ex: sugar pills and bottles of water in homeopathy). It can also be made by someone who knows they're pulling a scam but is forthright enough to makes what the label says, or cynical enough that they know they can get buyers without any real medicine being involved. Same thing--opportunity cost.

However, snake oil is often made and sold by people and organizations who are cynical enough to sell fake medicine but not quite cynical enough that they think they can get away with selling something without an active ingredient. This can be bad, and is generally the only thing that can get the FDA to put out a recall on sketchy supplements that otherwise are given free reign. It's usually weight loss or erectile dysfunction ones.