Instruct: Classify Amazon reviews into positive or negative sentiment
Query: Dangerous and Expensive

I was wondering why I just didn't feel well after a night of using my humidifier with this product in it. I'd wake up feeling like I had bad allergies or a cold (head stuffed, nose clogged and a general, tired feeling). Plus, I don't understand why this company charges so much. It costs $6.99 in stores and on other websites. I think a drop or two of Calgon water softener might prove safer than this toxic product.