Bests & Worsts Reviews from Amazon

I have a 6 year old 7 pound chihuahua. Have always used a cheap W-M brand of topical flea treatment, but decided to look online to see what was the number one recommended repellent for small dogs. K9 Advantix II came up on pretty much every list, so I ordered a two pack from Amazon. It arrived this past Friday 5-25-18. Had just given him a bath the day before so decided to go ahead and treat him. Within hours he was acting irritable, constantly doing the dog shake, and acting like he was uncomfortable. By the next day, Saturday he was still acting uncomfortable in his skin, still doing the dog shake at least every few minutes, scratching and not his usual energetic playful self. Now spring forward to Monday, Memorial Day, still having the same symptoms, but now vomiting any time he eats. Has vomited three four times that day. Now Tuesday morning, vomited in the middle of the night, still a little lethargic, not playful, still uncomfortable in his skin. Decided to look online for other complaints and have found hundreds of nearly identical stories. Will NEVER purchase this product again. Amazon, per their usual amazing customer service, issued me a full refund. I would not recommend this product to anyone who loves their dog.