There are no evidence-based scientific reports available on efficacy of garlic (either topical or oral) on fleas. Therefore I cannot predict its efficacy and safety for controlling fleas. It is unlikely to be as effective as currently available approved anti-flea products. However, there are some health benefits to pets reported when fed at recommended level in the food. But, garlic can be toxic and unpalatable to dogs when fed excessively.
Question by - K Suresh, Hyderabad