A high quality once a month topical dog treatment that will repel:

No large dog owner should be without the Advantix 12 Pack for Large Dogs between 10 and 25 kg (22-55 lbs.) Like other Advantix brand products, the large dog formula is completely water proof and continues to be effective after bathing or swimming. Not only will it repel and kill insect intruders, but it will even efficiently and effectively stop bites from all three of the aforementioned unwanted guests.

Just make sure to keep this product away from cats or other pets, as exposure or ingestion is known to cause serious health issues.