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Seresto vs Dewel: We Asked a Vet (2023 Update)

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By Dr. Iulia Mihai

seresto vs dewel

Vet approved

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Written by

Dr. Iulia Mihai

DVM MSc (Veterinarian)

The information is current and up-to-date in accordance with the latest veterinarian research.

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Both Seresto and Dewel offer protection against fleas and ticks for cats and dogs. Also, both products come in the form of a collar and work for 8 months, so you will not need to change the collar often or apply antiparasitic products monthly, as in the case of other products.

Dewel is made from natural ingredients like eucalyptus, cedarwood, citronella, and lavender. However, the substances found in Seresto collars are proven to be quite effective in killing and preventing external parasites, while Dewel seems to only keep them at a distance.

So, if you want an antiparasitic product with long-lasting action, choose either of these two products, but bear in mind that while Seresto is more expensive, it also kills fleas (including flea eggs and larvae), lice, and ticks.


At a Glance

Let’s see what the best option for your dog or cat is.

  • Kills and repels fleas and ticks
  • Water-resistant formula
  • Effective on contact
  • Available in two sizes for small and large dogs
  • Separate product for cats
  • 7–8-month action
  • Easy to use
  • Pricey
  • Repels fleas and ticks
  • Water-resistant formula
  • One size fits all, including cats
  • 7–8-month action
  • Easy to use
  • Inexpensive

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Overview of Seresto

Seresto collar

Seresto is an antiparasitic collar for dogs and catsthat is effective against fleas, lice, and ticks for 8 months. This product is infused with insecticidal substances, which are released on the skin and fur of your dog or cat for 8 months. It is effective on contact even before the fleas and ticks have had time to bite your pet.

Seresto is available in two sizes for dogs (small and large), and cats also have a product specifically for them. The minimum age for dogs is 7 weeks, and for cats, it is 10 weeks. No prescription is needed.

Like any other product, Seresto can cause allergic reactions. Also, some pets can get pesticide poisoning. You’ll need to take this aspect into account when deciding on the best product for your pet.

  • Non-greasy collar
  • Odorless and water-resistant
  • Mess-free application
  • Kills pests and prevents flea, lice, and tick infestations
  • Treats adult fleas, larvae, and eggs
  • Protects pets from tick-borne diseases (e.g., Lyme disease and babesiosis)
  • Long-lasting treatment
  • Work up to 8 months
  • Comes in two sizes for small and large dogs
  • Separate product for cats
  • For small dogs, minimum weight: 18 lbs. (8 kg)
  • For large dogs, minimum weight: 18 lbs. (8 kg)
  • Can cause allergic reactions in sensitive dogs, such as vomiting, diarrhea, redness on the skin, swelling of the face, abnormal behavior, and lethargy
  • Can lead to insecticide poisoning (excessive drooling, small pupils, diarrhea, vomiting, colic, difficulty breathing, muscle spasms and weakness, lack of coordination, and seizures)
  • Cannot be used on puppies less than 7 weeks old
  • Efficacy reduced with water immersion
  • Pricey

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Overview of Dewel

Dewel collar

Dewel is an antiparasitic collar for dogs and cats that is effective against fleas and ticks for 8 months. However, the manufacturer’s website states that this product only repels fleas and ticks. It does not mention anything about being effective on lice or about killing fleas and ticks.

Dewel is a natural product made out of natural ingredients that keep fleas and ticks at bay. The strong smell combination keeps these pests away. It comes only in one size that fits all pets, including cats. It can be used on all breeds and ages. No prescription is needed.

Like any other product, Dewel can cause allergic reactions or intoxicate pets, especially cats that are sensitive to essential oils. Also, citronella has the potential to cause allergic skin reactions on contact and can be dangerous to pets if ingested. Take these factors into account when determining the best product for your pet.

  • Made with natural ingredients
  • Repel fleas and ticks
  • Long-lasting treatment
  • Easy to use
  • One size fits all
  • Works up to 8 months
  • No age or weight limit
  • Does not kill fleas or ticks (no mention about killing external parasites at all)
  • Does not work on lice
  • No separate product for cats
  • Can be dangerous to cats
  • Can cause allergic reactions in dogs and cats, such as vomiting, diarrhea, redness on the skin, swelling of the face, abnormal behavior, and lethargy
  • Made in China


What Are the Differences Between Them?

Woman wearing a collar for dog, kill and repel tick and flea
Image Credit: Chutima Chaochaiya, Shutterstock

Active Ingredients

For its active substances or ingredients, Seresto contains imidacloprid 10% and flumethrin 4.5%, two highly effective insecticidal substances. Dewel contains only natural ingredients, including cedarwood, lemon eucalyptus, citronella oil, and lavender. It’s not known in what concentration each ingredient is found.

Target Parasites

The common external parasites that Seresto and Dewel act upon are:
  • Fleas: Ctenocephalides canis and C. felis
  • Ticks: deer ticks (Ixodes spp.), American dog ticks (Dermacentor variabilis), brown dog ticks (Rhipicephalus sanguineus), and Lone Star ticks (Amblyomma americanum)

Seresto also kills and repels biting lice (Trichodectes canis). This product can kill fleas’ larvae and eggs.

Interaction With Other Medicinal Products

For both products, there are no known interactions with other drugs or substances. However, it is best to contact your vet if you have any suspicions.

Duration of Action

Both products offer a long-lasting effect (7–8 months).


Both products are available as water-resistant adjustable collars. Seresto is non-greasy and odorless and comes in two sizes for dogs and a separate product for cats. Dewel has a strong smell and is one size fits all, including cats. If your pet does not like the smell, stop using the product.

Optimal Weight and Age

For small dogs and cats, the minimum weight for Seresto should be up to 18 lbs. (8 kg), and for large dogs, it should be over 18 lbs. The minimum age for using Seresto is 7 weeks for dogs and 10 weeks for cats. Dewel can be used for any breed and any age, as the manufacturer’s website states.


Although Dewel is cheaper than Seresto, it does not kill ticks, lice, adult fleas, flea larvae, and flea eggs. Dewel only repels fleas and ticks, which may still end up in your pet’s bedding and home. If the flea eggs and larvae thrive in your home, you will have to buy additional products to get rid of them.

woman wearing the cat a flea and tick collar
Image Credit: Inga Gedrovicha, Shutterstock

What the Users Say

Most people are satisfied with Seresto and Dewel, calling them effective against fleas and ticks. Seresto is odorless, and no humans or pets complain about it being smelly. Dewel has a smell that some pets may find too strong. Both products are mess-free and people love them.


People are quite satisfied with Seresto, having only words of praise. A few complained that even though they had good results in the past, they recently have not seen the same results, as their dogs are still scratching weeks after they applied the collar. People who have used Seresto on cats are also satisfied with the product. This product significantly reduced flea-and-tick populations in the first 24–48 hours. That said, some individuals have complained that the product does not work, especially for breeds with long or thick fur, which is understandable because the collar does not come into contact with the skin as well.

Some dog owners have also reported adverse effects in their pets, such as gastrointestinal problems, loss of appetite, lethargy, or itching at the collar site. Furthermore, the insecticidal substances that Seresto uses can be harmful to your pet, especially if they’re sensitive. For this reason, it is recommended to monitor your four-legged friend as soon as you put the collar on them and report any changes that you notice to the veterinarian.


Most dog owners highly appreciate Dewel. However, this product has been reported to cause scabs and neck irritation. In the case of cats, many people have reported adverse effects.

People also complain that Dewel has no effect, finding fleas on their pets even after a month of use. There are other complaints that Dewel does not stop the life cycle of fleas.

Some owners have complained about the strong smell that the collar has.

Blue anti tick and flea collar on cute dog
Image Credit: Alexei_tm, Shutterstock

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Overall, both Seresto and Dewel do what they promise: They are effective against fleas and ticks. However, Seresto repels fleas and ticks and treats them. It also kills and prevents lice, flea larvae, and flea eggs. Unlike Dewel, Seresto is made from insecticidal substances, which have proven to be extremely effective (but can cause health problems for some pets). Dewel is made from four natural substances, but these can also cause problems for sensitive cats or dogs. Both products can cause allergic reactions in pets.

Seresto and Dewel are available in the form of water-resistant adjustable collars. Seresto is available in two sizes for dogs (under 18 lbs. and over 18 lbs.) and a separate product for cats, the minimum age being 7 weeks for dogs and 10 weeks for cats. Dewel can be used on dogs and cats of all breeds and ages. Seresto is odorless, and Dewel has a strong smell that can become annoying both for the pet and the owner. Both products are effective for 7–8 months.

Featured Image Credit: Luisella Planeta Leoni, Pixabay

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