Johnsons4Fleas Spot-On


Liquid Spot-on

Active ingredient


Frequency of use

Every 4 weeks

Minimum age

8 weeks


Adult fleas (cats and dogs), Immature fleas (cats and dogs) and Biting lice (dogs)

What is Johnsons4Fleas?

Johnsons4Fleas is a non-prescription spot-on (topical) treatment for cats and dogs. Johnsons4Fleas treats fleas and biting lice in dogs. It also treats fleas in cats. Johnson4Fleas treatments are packaged in small pipettes that can be applied on the  back of a cat or dog’s neck. Each treatment lasts for 4 weeks.

What does Johnsons4Fleas do?

The key active ingredient in JohnsonsforFleas is imidacloprid. Imidacloprid affects the nervous system of fleas and biting lice by disrupting the ability to transmit nerve impulses. This leads to paralysis and, ultimately, the death of the fleas and biting lice.
After application, imidacloprid is absorbed through the skin and enters your pet’s bloodstream. It is then distributed throughout your pet’s body. This provides a sustained release of imidacloprid, ensuring ongoing protection against fleas for four weeks.
When a flea bites, they ingest some imidacloprid. They are killed within 24 hours, before they can mate and lay eggs.

What is Johnsons4Fleas for?

For Cats and Dogs:

Treatment and Prevention of Fleas: Johnsons4Fleas is effective at treating and preventing fleas in both dogs and cats. By disrupting the flea life cycle, it not only eliminates existing adult fleas but also prevents adult fleas from mating and producing flea eggs.
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.

For Dogs:

Treatment of Biting Lice: Although biting lice infestations are rare, Johnsons4Fleas can treat this.

What are the possible side effects with Johnsons4Fleas?

Johnsons generally well-tolerated, but as with any medication, there can be potential side effects. Pet owners should be aware of these side effects. Potential side effects of Johnsons4Fleas include:

  • Temporary Irritation at Application Site: Some pets may have mild and transient irritation at the application site. Signs include redness, irritation and temporary hair loss at the application site.
  • Hypersalivation (Excessive Drooling): Occasionally, pets may exhibit excessive drooling after application. This happens if they have licked it off. If they’ve licked off a small amount, it’s a temporary reaction to the unpleasant taste of the product.Owners should prevent pets from grooming the treated area immediately after application. Placing a cone on a treated pet until the treatment dries is a good way of doing this.
  • Gut upset: If dogs lick sufficient quantities of the product or if it is accidentally given orally, gut upset may occur. Signs include vomiting or diarrhoea.
  • Allergic Reactions: While uncommon, some pets may have an allergic reaction to the active ingredients in Johnsons4Fleas. Signs of an allergic reaction can include swelling, itching, redness or difficulty breathing. Talk to your vet immediately if you see any of these signs in your pet. Breathing difficulty is a serious problem that needs emergency attention.
  • Nervous system issues: These side effects 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 Johnsons4Fleas safely

  1. Follow instructions carefully: Always use Johnsons4Fleas exactly as your vet has prescribed, or according to the instructions on the label. This includes the right dose and frequency.
  2. Never split doses: Always use the product in the right weight range for your pet. Never try to split a larger dose between several pets.
  3. Check the species: Never give a dog dose to a cat, or vice versa. The doses will likely be incorrect. Too low a dose will be ineffective, and too high a dose will be toxic
  4. Storage and Handling: Store Johnsons4Fleas according to the instructions on the label, usually in a cool and dry place. Make sure it’s out of reach of children and pets.
  5. Report any accidental overdose to your vet immediately: If you have mistakenly given too much Johnsons4Fleas, report it to your vet as soon as you realise the error. They will calculate whether the overdose is likely to cause a problem and inform you of next steps. They may recommend blood tests, treatment or monitoring, depending on the severity of the overdose.
  6. Part fur and apply to back of neck: The product needs to be placed high enough that the pet cannot lick it off. The back of the neck is usually the best place, a little higher than the shoulder blades. In larger dogs, it’s recommended to split the dose down the back line – dogs will need to be prevented from licking until the treatment is dry. 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 until the treatment has dried. Also, for optimal absorption, the fur has to be parted and the product applied to bare skin.
  7. Apply Johnsons4Fleas to intact skin: Johnsons4Fleas should be applied to intact skin. Do not apply on broken or irritated skin.
  8. 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 ingestion. If necessary, continue applying the second half of the dose in a new spot.
  9. Do not allow your dog to swim in lakes: Although Johnsons4Fleas remains effective if a pet baths after treatment, Imidacloprid is harmful to aquatic organisms. Your pet should not be allowed to swim for at least 48 hours after having Johnsons4Fleas applied.
  10. Do not bathe your dog frequently during treatment: Repeated baths may cause treatment failure. Speak to your vet about how frequently your dog should be bathed while on Johnsons4Fleas.
  11. Take care with furniture: This product may stain materials including leather, plastics, and fabrics. Do not allow pets to come into contact with these surfaces until the product is dry.
  12. Wash hands after applying product. Washing hands after use should help reduce accidental absorption and sensitivity. Some people are sensitive to the ingredients in Johnsons4Fleas. These people should not handle the product.
  13. Do not sleep with your pet in the same bed on day of treatment: This is to minimise accidental contact between you and Johnsons4Fleas. Be especially careful with children. Children should not play with pets or sleep in the same bed with them on the day of treatment.

Johnsons4Fleas FAQs

How long does Johnson’s Flea spot on take to work?

Johnson’s Flea spot on takes minutes to work and start killing fleas. Fleas are killed within one day, and further infestation is prevented for 4 weeks.

What is the active ingredient in Johnsons4Fleas Spot on?

The active ingredient in Johnsons4Fleas Spot on is Imidacloprid.

Why does spot-on flea treatment not work?

Sometimes, spot-on flea treatment does not work for many reasons (e.g. too low a dose, improper application, too frequent bathing). If Johnsons4Fleas does not work on your pet, speak to your vet to try and narrow down the cause.

Johnsons4Fleas 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 Johnsons4Fleas 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.