Product review (5 stars): don't listen to the negative comments
first - this is a good product - i've used it for 2 months now. i like how it makes the air coming out of the humidifier smell fresher than it did before. haven't had any problems with algae (or anything else) growing in unit.
i have to make a point to say : THIS STUFF IS NOT TOXIC - IT DOES NOT HURT SKIN AT ALL. i read this a couple of times in other reviews and it's just not true.  i soaked my index finger in the unmixed solution right out of the bottle and experienced NO discomfort whatsoever. i also had no trouble in using the cap to measure out 2  caps of product to put in water. yes, on the back of bottle it does have warnings......just like ANY other chemical product. it DOES foam up some if you add the chemical early - simple solution....just add the product once all of the water is in.
if you're needing something to add to your humidifier water, don't hesitate to order this. it's a good product.