A vet tech friend of mine recommended neem oil(origins indian tree) for prevention of ticks and fleas. Said it's been used for hundreds of years on humans and more recently on dogs..with great results...i've recently become frustrated with my frontline. It doesn't seem to work that well(one or two ticks a month) despite the high cost and who knows what type of adverse effect it has on my dog. Love to hear your opinions. Thanks

thanks steve, for the quick reply and great resource at pubmed.gov so what are our commercial products doing to our dogs? and us for that matter?

FYI regarding the other mentioned consituent:

Azadirachtin is a chemical compound belonging to the limonoids. It is a secondary metabolite present in the Neem tree seeds. The molecular formula is C35H44O16. Azadirachtin is a highly oxidised tetranortriterpenoid which boasts a plethora of oxygen functionality, comprising an enol ether, acetal, hemiacetal, and tetra-substituted oxirane as well as a variety of carboxylic esters. It is classified among the plant secondary metabolites.

Additionally, both secondary and tertiary hydroxyl groups and tetrahydrofuran ether are present. Inspection of the molecular structure reveals 16 stereogenic centres, 7 of which are tetrasubstituted. These characteristics explain the great difficulty encountered when trying to produce it by a synthetic approach. It was initially found to be active as a feeding inhibitor towards the desert locust (Schistocerca gregaria), it is now known to affect over 200 species of insect, by acting mainly as an antifeedant and growth disruptor. It fulfils many of the criteria needed for a natural insecticide if it is to replace synthetic compounds. Azadirachtin is biodegradable and shows very low toxicity to mammals, thus being environmentally sound.
This compound is found in the seeds of the Neem tree (0.2 to 0.8 percent by weight). Many more compounds, related to Azadirachtin, are present in the seeds as well as in the leaves and the bark of the Neem tree which also show strong biological activities. Azadirachtin is the only correct name for this compound e.g. azadirachtin A is incorrect.

http://en.wikipedia.org/wiki/Azadirachtin