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With so many excellent flea preventatives on the market and new ones arriving at what seems almost daily, it can be overwhelming trying to choose the best flea preventative for your pet. It will make life easier if we start by assuring you that there is no one preventative that is “the best.” We are very fortunate that today there are more weapons to fight fleas than ever before and they are, by and large, safer and more effective. So rather than focusing on the “best” let’s gain an understanding of the broader categories and routes of administration and arm you with information you can use to make the right choice for your pet. This is in no way meant to be exhaustive coverage of this topic or a list of all available products. Rather, it is meant to give you a basic understanding of the types available in easy to understand terms.


Before we begin, please note: Pay close attention to the species and size indications on the packaging. Products not specifically labeled for cats may be lethal if given to them. Also note that while most products are extremely safe, overdosing can still result in toxicity and possible death.


The first category is the pyrethrins/permethrins group. These are chemically similar to substances from plants such as the Chrysanthemum (which doesn’t mean non-toxic) and have been around for quite some time. When they first arrived they were extremely effective but over the years we are finding increasing resistance to their effects. They are commonly found in a wide variety of applications, from shampoos and dips, to flea powders, flea collars and even topical formulations (typically applied between the shoulders). They work well if the flea population you are fighting has not developed a resistance to them. The majority of over-the-counter products will contain these types of ingredients. Choose these products if you prefer shampoos or powders or if cost is the primary factor in your decision (though it may not be cheaper if you are dealing with a resistant population). Quite a few products in this group will also include some form of insect growth regulation to prevent immature fleas from developing into adults.


The second category is the topical flea preventive. The most common in this group are Frontline (and its off-shoots and generics such as Pet Armor) and Advantage (in all its various forms). These are applied topically and spread through the oils on the surface of the skin. For this reason, it is important to follow the directions for application closely. If you bathe your pet too near the application, either before or after, you may strip the oils from the skin and these products may not work properly. The primary ingredients tend to be fipronil (Frontline) or imidacloprid (Advantage) and they work very differently from one another. In very simple terms, fipronil works by overstimulating the nervous system of the flea, ultimately resulting in the death of the flea. Fleas can still bite during this time, though dead fleas don’t bite or lay eggs. Imidacloprid works by paralyzing the flea. Paralyzed fleas cannot bite and quickly die. Both products come in a variety of formulations which may add tick prevention, protection from mosquitos, lice, etc. Check the packaging to be sure you have the coverage you are seeking.
The third category is oral flea preventives. This includes products such as NexGard, Bravecto, Sentinel, Comfortis, Trifexis, Simparica, etc.. They are most commonly given either monthly or every 3 months and are extremely effective. Fleas do have to bite to get the product and the most common side-effects are vomiting and diarrhea, which often abate after the first couple of doses. They should be used with extreme caution in patients prone to seizures or with other neurologic abnormalities. The benefits include less resistance than other products and they are not affected by bathing or excess swimming. Some are combined with heartworm preventive, tick preventives, etc. My personal preference is to separate the heartworm preventive from the flea/tick product. While we do see some resistance to various flea products (and can expect resistance in the future), we really do not see resistance to heartworm preventive to any great degree. Be aware that if you combine the two and encounter a resistant population of fleas, you may have several months of product that you will either have to discard or will have double medicate with another flea product. For those seeking the convenience of an all-in-one product, we see less resistance to the oral formulations than to the topicals.


The final category we will cover is collars. Previously flea and tick collars have had marginal effectiveness at best. But new collars such as Soresto are proving quite effective for up to 8 months. They are a convenient way to provide flea & tick control but carry a price tag similar to 8 months of coverage from oral or topical preventives.
In choosing a flea preventive, consider the specifics and needs of your pet. If cost is the primary concern, the pyrethrins/permethrins group may be your best choice with a sensitive flea population. For those with a pyrethrin/permethrin resistant flea population, or who are seeking a less expensive monthly flea product, topical can be an excellent choice. In particular, pets with a flea allergy typically do quite well on Advantage products due to the lack of biting from the paralyzed fleas. For pets with skin disease, those who require frequent bathing, who swim regularly or who have shown sensitivity to topicals, an oral flea preventive or collar are your best bets. In all cases, I strongly encourage you to consult with your veterinarian to help guide you in selecting the best product for your pet. They will help you choose the product that is suited for your needs, your pet’s needs and your budget.