I live in the south where mosquitoes are a problem. My dog is 7 years old, 5 pounds. She has taken heartguard when she was little, something else for a little while, then interceptor for a long time, then quadriguard twice (she threw up after the quadriguard both times), and now she is on sentinel. I do not want her ingesting a toxin every 6 weeks, but I also do not want her to get heartworms. The only natural HW medicines I have found are Heart Worm Free and a homeopathic nosode. But HWF has alcohol and cyanide and the homeopath has alcohol. Any kind of alcohol is very hard on a dog's liver and any kind of cyanide it toxic.
What is a safe, natural heartworm preventative? Thank you 
