Only Natural Pet HW Protect Herbal Formula Effective herbal alternative to chemical heartworm prevention methods Intended for use as a preventative during mosquito season as part of a comprehensive heartworm control program Uses herbs to reduce the likelihood of mosquito bites to lower your pet's risk of becoming infected, and helps eliminate existing larvae-stage parasites in the bloodstream Made in an FDA-approved facility with human-grade ingredients Only Natural Pet brand products are 100% Guaranteed!