A random thought...
If someone is taking alternative medicine, is it right to mention that is the placebo effect at work? After all, if it is indeed the case that the solution is having a positive effect then what value is there is destroying the one thing that could possibly work?
To tell someone that they are taking a placebo is to destroy its effects. That is, of course, unless they don't believe you. Then telling them will have no effect whatsoever and the placebo effect remains!
Though chances are that if someone is taking alternative medicine (an oxymoron if there ever was one) then they aren't going to suddenly stop believing in its healing powers. Just hope that if it's a loved one that such negative reinforcement between treating illness and quack cures will mean that if the condition is serious they'll seek tested medical treatment.