Guest Post: The Pros and Cons of Spot-On Flea Killers - The Trupanion Blog
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Guest Post: The Pros and Cons of Spot-On Flea Killers

The following is a guest post provided to Trupanion from Bernice Spradlin. Bernice is an avid hiker and runner. She works at a gym in Brooklyn, New York, where she gets great inspiration for her freelance writing. In her off time, you can often find Bernice jogging the East River path along the waterfront and enjoying a cuddle and a weepy movie with her pug, Molly. Bernice can be contacted at

Fleas are a pesky parasite. Not only did they affect the health of my precious pug, Molly, they also infested my home. Everything from our bed sheets to our bath mat had to be treated. However, when the vet gave Molly something called a “spot on” flea killer, I thought that was the end of the infestation. Sadly, I couldn’t have been more wrong.

The fleas were only banished temporarily and poor Molly suddenly developed a sore, runny red eye along with a nasty rash. I had no idea what to do so I applied an anti-bacterial ointment for humans that I purchased via an online Canadian drug store. When her condition worsened, I finally took Molly to the emergency vet clinic. The vet said that although negative reactions are rare, they can occur with small and medium sized dogs like Molly with sensitive skin. She treated Molly with a topical ointment for the rash and antibiotics for her red eye.

Here is how the emergency vet explained fleas and flea killer to me:

This is what happens when your pet gets fleas…

It’s difficult to rid your dog or cat and your home of a flea infestation. Fleas (females only) begin laying eggs on their host cat or dog within the first 24 hours, and once the eggs hatch, the larvae can remain inactive for weeks until they mature into adult fleas.

When your cat or dog gets fleas they can lose a dangerous amount of blood. In addition, itching and scratching from fleas can cause serious skin infections. If you notice your pet scratching a lot, look through their fur to their skin for tiny dark brown bugs about the head of a pin. Once you spot fleas, you need to take action immediately as a pet with fleas can get very sick or even develop tapeworms at sites of infection on the skin. To fight a flea infestation, contact your veterinarian immediately.

What vets commonly recommend for treating fleas…

Many vets will recommend what’s called a “spot on” flea killer as opposed to an oral flea medication. These monthly topical treatments are administered via a tube and applied to your pet’s skin—directly between the shoulder blades or near the upper spine so that the animal can’t lick it off or dig at the area. Topical flea treatments are absorbed by your pet’s oil glands, which then distributes the flea killer throughout the skin and hair.

The most common topical flea treatments include:

1. Advantage: This “spot on” flea treatment is touted for an ingredient called imidacloprid that affects the nervous system of the flea, causing paralysis and death within 12 hours. It also paralyzes them from biting your pet within five minutes of application. When you imagine that one flea can lay a few dozen eggs every day—the sooner you kill them, the better!

The pros of Advantage…

  • This product is applied only once every 4 weeks (others require weekly applications)
  • Less applications means it costs less and lasts longer
  • Advantage has no bathing restrictions, which is preferred by owners with pets that are outside a lot
  • It can be applied anytime of the month
  • Application instructions are easy

The cons of Advantage…

  • It kills only fleas, not ticks
  • This product takes a few days to completely absorb into the pet’s skin so it can be dangerous if children or other pets are exposed
  • Skin sensitivities have been known to result—if so, contact a veterinarian immediately
  • Advantage is very dangerous if your pet ingests it
  • Causes eye irritation in humans and is harmful if swallowed

2. Frontline (or TopSpot): This “spot on” oil takes advantage of the natural oils in your pet’s body to spread itself evenly over the skin and hair.

The pros of Frontline…

  • Very effective flea and tick killer
  • Easy to apply

The cons of Frontline…

  • Your pet must be bathed 3 days prior or 3 days after Frontline is applied
  • The packaging is complicated and a pain
  • Frontline is not a tick repellant, so ticks can continue to attach to your pet before they die (which puts pet at risk of Lyme disease)
  • The topical oil takes a while to absorb, so you must keep children and other pets at a distance
  • Pets may experience irritation at the site of the Frontline application—if it persists, consult your veterinarian immediately

3. Revolution: This anti-parasite topical treatment protects pets against fleas, ticks, heartworm, Sarcoptic Mange and ear mites.

The pros of Revolution…

  • Ideal for pets with multiple infestations and parasites
  • Protects against heartworm disease
  • Easy application

The cons of Revolution…

  • Again, this topical treatment takes a while to absorb, so other pets and kids should be kept away from your pet for at least one day
  • Side effects can include hair loss at the site of application, appetite loss, vomiting, diarrhea, drowsiness, increased heart rate and muscle tremors in pets

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