How Does Flea Medicine Work

How Does Flea Medicine Work


Flea medicines work and stop existing infestations of ticks and fleas by directly attacking their central nervous system. They poison and affect the insects as soon as they come in contact with it, but they don’t kill them immediately. The neurotoxins give the infected fleas time to return to their nests, resulting in the infection of other fleas at the nesting site. Flea medicine is harmful to insects in small doses but is absolutely safe for your pet.

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Does your dog have fleas?

Fleas are undoubtedly annoying, but it’s not always easy to spot signs of their infestation, especially if you’ve never dealt with the problem before. Following are some things veterinarians recommend looking out for:

  • Abnormal biting, licking or scratching

Fleas are arthropods and depend on pets’ blood as a food source. They usually set up their nests or habitat in hard to see and reach places, like the tail, head, neck, groin, or armpits. Scratching, licking, or biting at these places, generally, indicate the presence of irritating parasites like ticks and fleas.

  • Unusual red patches of skin

Some cats and dogs are allergic to flea bite saliva. These allergic reactions are not necessarily exclusive to the bitten body part, but flea bite hypersensitivity can result in lesions or rashes on any part of the body.

  • Hair loss

Alopecia, or hair loss, can be due to a number of things, including an adverse reaction to flea bites. Cats and dogs may also pull out their own hair because of the continuous licking and biting of the flea bite areas. The severity and pattern of hair loss are also vital for the right treatment plan and diagnosis. 

  • Pale Gums

Pale gums are a common symptom of anemia which can also be an indication of serious flea infestation in your pet. This is because the number of new red blood cells produced by your pet’s body is not enough to counter the blood loss caused by the fleas.

  • Flea dirt

Flea dirt is basically flea feces comprising of digested blood. If you notice any small reddish-brown or black specks on your pet’s body or around your home, it can be a sign of fleas. To make sure that it is flea dirt and not regular dirt, you can wet any of the black specks that fall off your dog using a regular water sprayer. If the specks turn a dark reddish-brown color, you need to apply flea medicine immediately. You can buy the medicine online from; the one stop for all your pet needs!

How does flea medicine work?

Once applied, flea medicine is absorbed through your pet’s skin and starts circulating into the bloodstream. Due to this, flea medicine treats ticks and fleas throughout your pet’s body and not just on the area of application. By being absorbed into your pet’s bloodstream, some medicines also prevent and treat internal parasites like heartworm, hookworm, roundworm, and even ear mites.

Commonly used ingredients in flea medicines and how they work.

  • Pyrethrins

One ingredient most commonly found in flea control medicines for pets is Pyrethrins. They affect an insect’s nerve cell, disrupting its normal function and causing it to transmit and fire non-stop impulses. This consequently leads to the insect’s death. Pyrethrins contain low toxicity, making them safe to use in pets or any other mammals. The ingredient is directly applied to the animal’s hair or skin to not only control and kill fleas, but also mites, ticks, lice, and mosquitos.

Pyrethrins are unstable and are unable to withstand extended exposure to air, moisture, and light. To protect and prevent the ingredient from breaking down, it is generally combined with other chemicals.

  • Imidacloprid

A topical insecticide, Imidacloprid works by blocking and obstructing the nervous system conduction in insects. Most of the adult fleas are killed within 24 hours of application, further reducing the chance for them to reproduce. The ingredient is usually combined with an oily carrier, so that when applied, it can spread out over the entire body, especially in the hair follicles. There, it continues to kill adult fleas, eggs, and larvae for approximately a month. 

  • Selamectin

A chemical which kills both external and internal fleas, Selamectin works by blocking nerve signal transmissions. Absorbed into the pet's bloodstream through the skin, the ingredient is applied as a spot-on. It is not only used to kill and treat intestinal parasites, but it also protects against ticks, fleas, eggs, heartworm disease, and some mites.

  • Dinotefuran

Dinotefuran is an ingredient which kills fleas and ticks on contact. It interferes with the insect’s nerve signal conduction, killing all stages of the flea life cycle.

  • Insect Growth Regulators

Also known as Juvenile Hormone Analogs, Insect Growth Regulators (IGRs) are chemicals which affect the development of larvae. The ingredient makes it impossible for them to develop into fully-grown fleas, resulting in them being unable to reproduce. The most common insect growth regulators found in flea medications include Pyriproxyfen and (S)-methoprene.

How oral flea tablets work

Oral tablets are sometimes preferred over spot-on flea medicines, especially by parents of small children. After applying spot on, parents need to quarantine their pet, so their child won’t rub his/her hands on the medicine. However, with oral tablets, physical contact with the medication is not a concern. The most common ingredients used in oral flea medications include:

  • Spinosad

Lasting a full month, Spinosad quickly kills fleas and prevents future flea life cycles.

  • Nitenpyram

The chemical only kills adult fleas but does not prevent future infestations.

  • Lufenuron

Lufenuron works in the same way as insect growth regulators. It prevents future infestations by affecting the development and growth of eggs and larvae, rendering them unable to reproduce.

How flea sprays work

The ingredients in flea sprays work in the same way as spot-on flea medications. The neurotoxins affect the nervous system, killing the fleas quickly while growth inhibitors prevent the development and growth of larvae and eggs, consequently preventing future infestations. The most common ingredients used in dog flea sprays include:

  • (S)-methoprene
  • Pyrethrins
  • Fipronil

However, make sure you use great caution when using sprays, especially with children around, as it significantly increases the chances of physical contact and inhalation of chemicals.