Stronghold Spot-On


Liquid Spot-on

Active ingredient


Frequency of use

Every 4 weeks

Minimum age

6 weeks


Fleas (adult), fleas (immature), ear mites, roundworms, biting lice, scabies (in dogs) and hookworms (in cats). Stronghold also prevents heartworm and fleas (adult and immature).

What is Stronghold?

Stronghold is a topical (‘spot on’) antiparasitic drug that is manufactured by Zoetis. The active ingredient in Stronghold is selamectin. Stronghold is only obtainable with a prescription. Stronghold comes in pipettes, which are applied to the skin on the back of your pet’s neck (between their shoulder blades). Vets often recommend Stronghold to be applied at regular intervals, as a routine preventative against various parasites.

What does Stronghold do?

Stronghold contains one active ingredient: Selamectin.

Mode of Action:   By acting on glutamate gated chloride channels the parasites’ nervous system, Selamectin disrupts the normal electrical activity of the nervous systems and  interferes with muscle activity. This causes the paralysis and death of the parasites. 

Administration: Stronghold is applied topically to the skin, typically between the shoulder blades of the pet.

Absorption and Distribution: After application, selamectin is absorbed through the skin and enters the bloodstream. Selamectin is then distributed throughout the body, reaching target tissues where parasites reside (such as the skin and hair follicles).

Metabolism and Elimination: Selamectin is broken down (metabolised) in the liver. These metabolites are then eliminated primarily through the faeces, with a smaller portion excreted in the urine.

Duration of Action: A single application of Stronghold provides protection against a range of parasites for about one month. It’s important to follow the recommended dosing schedule for ongoing efficacy.

What is Stronghold for?

Stronghold can used in a number of situations:

For Cats and Dogs

  • Treatment and Prevention of Fleas: Stronghold is highly effective in controlling fleas, preventing infestations in both dogs and cats. By disrupting the flea life cycle, it not only eliminates existing adult fleas but also prevents the development of flea eggs and larvae.
  • Heartworm Prevention: Stronghold provides crucial protection against heartworm disease, a serious and potentially fatal condition transmitted through mosquito bites. Regular use of Stronghold helps ensure that your pet remains heartworm-free.
  • Roundworm: Stronghold targets and treats roundworms in cats and dogs. This reduces the intestinal worm burden and contributes to their overall health.Ear Mite Treatment:  Stronghold serves as an effective treatment for ear mites. Ear mites can cause discomfort and irritation, and Stronghold helps eliminate these parasitic pests, promoting ear health in feline companions.

For Cats

  • Hookworms: Stronghold targets and treats hookworms in cats. This reduces the intestinal worm burden in cats and contributes to their overall health.

For Dogs

  • Treatment and Control of Sarcoptic Mange: For dogs suffering from sarcoptic mange, a skin condition caused by mites, Stronghold is a valuable solution. It aids in the treatment and control of mange, helping to alleviate skin issues and improve overall comfort.

Stronghold is a versatile and comprehensive parasiticide that supports the overall health and well-being of dogs and cats. However, do note that Stronghold is not effective against ticks or certain types of worms (e.g. tapeworm) Thus, do ask your vet about the preventative that’s best suited to your pet’s lifestyle. In addition, do follow your vet’s recommendation regarding the dosage and application frequency. This ensures optimal protection against a variety of parasites.

However, if you want to banish fleas for good,  it’s important to rid the environment of fleas as well. Even if you get rid of fleas on your pet with preventative, fleas can live in a house for several months and re-infect your pet. Fleas can also bite humans! Speak to your vet about ways to rid your house of fleas.

What are the possible side effects with Stronghold?

Stronghold are usually mild or rare, pet owners should know about them before using Stronghold. If your pet experiences side effects, tell your vet – who will then inform the manufacturer. Potential side effects include:

Transient Skin Reactions: Some pets may experience mild and temporary skin reactions at the application site, such as redness, itching, or a tingling sensation. These reactions are usually self-limiting and resolve on their own.

Hypersalivation (Excessive Drooling): Excessive drooling may occur, especially if the pet licks the application site. It’s advisable to prevent pets from grooming the treated area immediately after application. A cone may be placed on the pet to prevent them from licking the treated area(s) if necessary, until the treatment dries.

Temporary Behavioral Changes: Pets might exhibit temporary changes in behavior, such as increased scratching or rubbing at the application site. These changes are typically short-lived.

Gastrointestinal Upset: In rare cases, pets may experience mild gastrointestinal upset, including vomiting or diarrhea. If these symptoms persist or are severe, consult your veterinarian.

Allergic Reactions: While uncommon, some pets may have an allergic reaction to the active ingredients. Signs of an allergic reaction can include swelling, itching, redness or difficulty breathing. If you observe any of these signs, seek veterinary attention promptly. Breathing difficulty is a serious problem that needs emergency attention.

Disturbance to pet’s nervous system: This side effect is rare, but very serious. Signs include incoordination, dilated pupils, salivation, trembling and/or even seizures. Contact your vet immediately if you see these signs. A seizure is a life-threatening emergency that requires immediate veterinary attention.

How to give Stronghold safely

  • Follow instructions carefully: Always follow the vet’s instructions (regarding the dose, frequency etc) when applying Stronghold to your pet. You need to know your pet’s current weight before applying Stronghold.
  • Never split doses: Always use the product with the right weight range for your pet. Never divide a bigger dose amongst multiple pets
  • Check the species: Never apply “Stronghold for Dogs” on a cat, or vice versa. The dose will likely be incorrect. Too small a dose will be ineffective, and too large a dose will be toxic.
  • Storage and handling: Store Stronghold according to the instructions on the label, usually in a cool and dry place. Ensure that children and other pets cannot access it.
  • Avoid contact with skin, eyes, hands and mouth: Wear gloves when applying Stronghold. If any of the product  gets onto your bare skin, wash it off immediately. Do not eat, drink, or smoke during application. If product gets into eyes, wash thoroughly and seek medical attention if symptoms persist. If the product is accidentally ingested, seek medical attention immediately. Avoid touching your pet with your bare hands until the product has dried.
  • Avoid sleeping with your pet in the same bed on the same day of treatment: This is to minimise accidental contact between you and Stronghold. Be especially careful with children. Children should not play with pets or sleep in the same bed with them on the day of treatment.
  • Part the fur and apply to skin on back of neck: The product needs to be placed high enough that the dog or cat cannot lick it off. The back of the neck is usually the best place, a little higher than the shoulder blades. Also, for optimal absorption, the fur has to be parted and the product applied to bare skin. If the dose is applied to a spot that’s low enough for a pet to lick off, a cone could be used to prevent licking. In larger dogs, the manufacturer recommends that you split the dose down the back line – dogs will need to be prevented from licking until the treatment is dry. 
  • Apply Stronghold to intact skin:  Stronghold should be applied to intact skin. Do not apply on broken or irritated skin.
  • Don’t apply too much in one spot: If you apply too much product in one location it may spill over, dripping down your pet and increasing the chance of them licking it off. If necessary, continue applying the second half of the dose in a new spot.
  • Do not allow your pet to swim:  Selamectin poisons aquatic wildlife. Therefore, do not let your dog swim in lakes for at least 48 hours after having Stronghold applied.
  • Tell your vet if you bathe your pet frequently: Pets may be bathed 2 hours after treatment. However, frequent bathing may cause the treatment to fail. If your pet needs to be bathed regularly, tell your vet. They may recommend an alternative preventative.
  • Take care with furniture: This product may stain materials (e.g leather, plastics, fabrics). Keep pets away from these surfaces until the product is dry.
  • Keep away from fires: Keep your pet away from fires or sources of ignition until the product has dried, or for at least 30 minutes (whichever is longer)
  • Report any accidental overdose to your vet immediately: If you have mistakenly given too much Stronghold, report it to your vet as soon as you realise the error. They may recommend blood tests, treatment or monitoring, depending on the severity of the overdose.

Stronghold FAQs

How often should I apply Stronghold to my pet?

You should apply Stronghold to your pet according to your vet’s instructions. Although Stronghold is usually applied every 4 weeks, your veterinarian may adjust the frequency according to your pet’s needs.

Can I use Stronghold on my puppy or kitten?

Yes, you can use Stronghold on your puppy or kitten. However, do not use Stronghold on puppies and kittens under 6 weeks of age.

Is Stronghold safe for pregnant or nursing pets?

Yes, Stronghold is safe for pregnant or nursing pets.

Can I apply Stronghold if my pet has sensitive skin?

If your pet has sensitive skin, consult your vet about non-topical preventatives.

What should I do if my pet licks the Stronghold application site?

If your pet licks the Stronghold application site, monitor your pet closely for side effects. Pets are more likely to experience side effects if they have swallowed Stronghold. Contact your vet immediately and follow their instructions. They will inform you about the signs to look out for, and whether to bring your pet to the vet or to monitor at home.

How long does it take for Stronghold to start working?

It takes a few hours for Stronghold to start working, although it may take a few days for Stronghold to reach peak efficacy.

Can I bathe my pet after applying Stronghold?

You can bathe your pet 2 hours after applying Stronghold. However, Stronghold is toxic to aquatic wildlife. Therefore, if your dog swims in lakes, wait at least 48 hours before reintroducing your dog to lakes. Furthermore, Stronghold treatment may fail if you bathe your pet frequently so speak to your vet about the optimal bathing frequency if your pet has to be bathed while on Stronghold.

Is Stronghold effective against ticks?

No, Stronghold is not effective against ticks.

Can I use Stronghold on senior pets?

You can use Stronghold on senior pets after checking with your vet. Your vet can help you to rule out health conditions in your senior pets that would increase the risk of side effects from Stronghold.

What should I do if my pet experiences irritation at the application site?

If your pet experiences irritation at the application site, tell your vet (who will inform the manufacturer). Irritation at the application site is usually mild and self-resolving within a day. If the irritation persists, your vet may ask you to bring your pet in for treatment.

Stronghold Datasheet

All drugs have a manufacturer’s datasheet, which gives information about the drug’s use and possible side effects. There is usually one in your Stronghold box, but if you have lost it you can click on the button below to be taken on an online version.

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Please note that the information contained herein is provided for informational purposes only. Although it has been written by a vet, we cannot consider the individual nature of your pet’s problems so it does not constitute veterinary advice. If you have questions about your pet’s medication or their health you should contact a vet, who will be able to help.