Article in English: Monthly topical treatments are among the most effective and most popular type of preventative flea medication for dogs.  You will need a veterinarian's prescription for most of these topical or "spot on" treatments. Apply a few drops or a small pre-measured vial of the flea medication where it tells you to. Some medicines tell you to apply between your dog's shoulder blades while others ask you to apply it in several different locations. Get the medication directly on your dog's skin and not on its coat. This medication kills adult fleas that land on the dog or bite the dog. It is usually effective for one month. Some products are also able to kill eggs, but not all products do so. The medication should be applied monthly on a year-round basis. If you live in an area that regularly reaches the freezing point during winter, however, you might be able to use the product less frequently during these colder weather months, since fleas will be inactive. Ask your veterinarian about preventative tablets that you can administer to your dog on a monthly basis.   Feed the pill to your dog once a month during a meal. Your veterinarian will need to prescribe the correct dosage to your dog based on its weight. When a female flea bites the dog after treatment, it ingests a chemical known as lufenuron. This gets passed to the eggs and prevents them from hatching. (It does not, however, kill the adult flea, so the results may take some time to see). As with any treatment, it's worth keeping an eye on how your dog reacts. Look at the place you put the treatment to make sure there is no reaction and do not use it again if the dog's skin goes red or sore.

Summary in Vietnamese:
Bôi thuốc hàng tháng. Cho chó uống viên trị bọ chét mỗi tháng.