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Bayer Animal Health
K9 Advantix II for Large Dogs
$79.98$79.99across 2 retailers
Model: 81520402Color: RedUPC: 724089204028
Lowest at Amazon
$74.95 at AmazonLowest at any Popular Retailer
$31.98 at 1-800-petmedsWhere to Buy
Prices last updated: May 12th 2026 7:35 pm
Pros
- •Effective against fleas, ticks, and mosquitoes without requiring pests to bite.
- •Considered safer than oral medications as it can be washed off if an allergic reaction occurs.
- •Seen as affordable and positively reviewed by some users.
- •Can be applied in small amounts over multiple spots on the dog's back for better distribution.
Cons
- •Can cause adverse reactions such as tingling, redness, itching, and severe allergic responses.
- •Not safe for cats; it is lethal to them.
- •Ineffective in preventing tick and flea infestations for several users, despite previous success.
- •Some dogs experienced discomfort, agitation, and even severe symptoms like seizures and skin irritation.
- •Noticed a decline in product effectiveness, prompting some users to switch brands.
Bottom Line
While Bayer K9 Advantix II offers broad-spectrum pest protection, it's crucial to monitor dogs for any adverse reactions, especially during the drying period after application. Some users report a decrease in effectiveness against fleas and ticks compared to previous batches. If your dog has a history of allergies or sensitivities, it might be wise to consult a vet before use or consider switching to an alternative product that's proven effective, such as a chewable treatment.
What Reviewers Are Saying
Criticized
not effective50%
caused allergic reaction40%
disappointed with effectiveness30%
temporary solution20%
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