I think Frank meant MSM rather than MSN which is methylsulfonylmethane (dimethylsulfon). This sulphurous organic substance is very useful for organism especially against any inflamnations, allergy, skin problems and problems with joints. I am taking it quite regularly but without any affect at my floaters. This substance is almost completely unharm for organism even in quite higher dosages. I am taking 2 grams per day if I don“t forget to take it. The chemical formula is CH3 - SO2 - CH3.