Cytopoint for Dogs: Anti Itch Injection — Side Effects, How It Works, Cost & Does It Make Dogs Sleepy? (UK)

Cytopoint Injection For Dogs

Cytopoint is a prescription injection given by your vet to relieve itching in dogs with atopic or allergic dermatitis. It works by targeting a single protein  IL-31  that triggers the itch signal, and most dogs feel relief within 24–48 hours of their injection. Effects typically last 4 to 8 weeks, making it one of the longer-acting options available without daily dosing.

It is generally well-tolerated. The most commonly reported side effects are mild and temporary a quieter dog for a day or two after the injection is the most frequent observation. It does not cause sedation, and there is no evidence linking it to liver damage or cancer. Neurological signs such as seizures are listed on the official UK product label as rare fewer than 1 in 10,000 dogs treated.

In the UK, a single Cytopoint injection typically costs £50–£100 depending on your clinic and your dog's weight. It is prescription-only, so it must be administered or prescribed by a vet.

This article covers how Cytopoint works, what the evidence says about its safety and side effects, how it compares to Apoquel, and what alternatives exist including topical treatments that support skin barrier repair.

How Cytopoint Works and How It's Given to Dogs

To understand why Cytopoint works and why it behaves differently from steroids or antihistamines it helps to think about what's actually causing your dog to itch in the first place.

In dogs with atopic dermatitis, the immune system produces a protein called interleukin-31 (IL-31). Think of IL-31 as a messenger that travels from the skin to the nerves, essentially delivering the message: scratch here. The more IL-31 floating around, the more intensely and constantly your dog itches.

Cytopoint is a monoclonal antibody  a purpose-built protein that acts like a targeted interceptor. Once injected, it travels through the bloodstream searching for IL-31 molecules. When it finds one, it binds to it and neutralises it before the "itch message" can reach the nerves. No message, no itch signal.

Most dogs start feeling relief within 24–48 hours, with effects typically lasting 4 to 8 weeks which is why it's given as a one-off injection rather than a daily tablet.

How is this different from other itch treatments?

The reason Cytopoint has a cleaner safety profile than steroids comes down to that first row it only interferes with one specific messenger rather than turning down the whole immune system. Your dog's ability to fight infections, heal wounds, and respond to illness stays intact. It's a much more precise approach, which is why many vets now consider it a preferred first-line option for dogs with moderate to severe skin allergies. 

How Cytopoint is Given: Cytopoint is administered through an injection given under your dog’s skin, similar to a vaccination. A veterinarian will determine the appropriate dosage based on your dog’s weight, ensuring they receive the correct amount for optimal effectiveness.

⚠️ Note for pet guardians: The manufacturer advises that pregnant women should avoid administering Cytopoint injections. If this applies to you, ask your vet or veterinary nurse to administer it at the clinic.

When to Give Another Injection: To determine when your dog needs another injection, you should monitor their scratching behavior. Once you notice your dog starting to scratch again, it may be time for the next Cytopoint injection. On average, re-administration is required every 4 to 8 weeks, depending on how long the effects last for your dog.

Other Considerations:

• Cytopoint is a prescription medication, meaning it can only be obtained with a veterinarian’s approval.
• It’s important to consult your veterinarian for advice on the safe administration of Cytopoint to ensure it's suitable for your dog’s specific condition.
• Pregnant women should avoid administering this product

Effectiveness and Duration Of Cytopoint

• At 2.0 mg/kg, a significant reduction in itchiness was observed within 3–5 hours post-treatment.
• The effect was dose-dependent, with results lasting 14, 28, and 42 days for doses of 0.125 mg/kg, 0.5 mg/kg, and 2 mg/kg, respectively (MDPI, 2024).
• Unlike steroids or immunosuppressants, Cytopoint for dogs works naturally with the immune system, making it an alternative to drugs like Apoquel.

Does Cytopoint Cause Cancer in Dogs?

This question comes up a lot in dog owner forums and Facebook groups, and it's completely understandable why. When a dog develops cancer after receiving Cytopoint, it's natural to wonder whether the two things are connected. So let's look at what we actually know.

The honest answer is: no current evidence links Cytopoint to cancer in dogs.

After nearly 10 years of widespread use since 2017, neither the European Medicines Agency, the UK's Veterinary Medicines Directorate, nor the FDA has flagged cancer as a safety concern for Cytopoint. That's a significant amount of real-world use across millions of dogs without a regulatory signal and regulators do act when signals emerge, as we saw with Librela in 2025.

There is one theoretical question that's worth being upfront about. IL-31, the protein Cytopoint blocks does have some role in the immune system beyond just causing itch. A reasonable person might ask: could blocking it long-term affect the body's ability to detect abnormal cells? It's a fair question. But here's the important context:

• Cytopoint only blocks one specific protein it doesn't switch off the immune system broadly the way steroids do, or even the way Apoquel does

• In clinical trials, dogs on Cytopoint showed no higher rates of cancer than dogs on placebo

• The 2025 long-term study of Cytopoint found owners were overwhelmingly satisfied and continuing treatment, with no cancer signal emerging

If your dog has previously had cancer, or there's a strong history of it in their breed, it's always worth raising with your vet before starting any new treatment not because the evidence points to risk, but because that conversation is always worthwhile with any medication.

Cytopoint Side Effects in Dogs & What the Evidence Says

While Cytopoint for dogs UK is generally considered safe, it is crucial to assess reported side effects:

1. Mild Lethargy:

Why it happens:
Cytopoint targets a protein (IL-31) involved in allergic reactions. Sometimes, when the body encounters this new protein, it reacts as if it's a foreign invader, causing a mild immune response. This can make some dogs feel tired or lethargic. This side effect usually goes away on its own as the body adjusts to the treatment. Similar reactions are seen in human medicine with other monoclonal antibody treatments. Cytopoint is not a sedative and does not cause drowsiness in the way antihistamines like Piriton do. Some dogs appear quieter for 24–72 hours after their injection most likely a mild immune response to the new protein rather than the drug itself. 

2. Gastrointestinal Upset (e.g., vomiting or diarrhea):

Why it happens:
When Cytopoint activates the immune system, it can cause mild inflammation, which might affect the digestive system. This can result in symptoms like upset stomach or diarrhea. The drug works by targeting IL-31, but it can also indirectly affect the gut’s immune system. This kind of reaction is rare, but it has been observed in studies of other monoclonal antibody treatments.

3. Allergic Reactions:

Why it happens:
Allergic reactions are uncommon but possible. If a dog’s immune system recognizes Cytopoint as something unfamiliar, it can trigger an allergic response, such as swelling, hives, or even more serious reactions. This happens when the immune system releases histamine and other chemicals. Some dogs may also have sensitivities to proteins similar to Cytopoint, leading to a stronger immune reaction. This is a risk with many monoclonal antibody treatments.

4. Neurological Signs (e.g., ataxia, convulsions, or seizures):

Neurological signs following Cytopoint injection are classified as rare in the official EU Summary of Product Characteristics — defined as occurring in 1 to 10 dogs per 10,000 treated [EU EMA Cytopoint SPC, updated 2023]. These reports come from post-marketing surveillance data (spontaneous reporting), not from controlled clinical trials, where no neurological events were observed in study populations.

Why this signal matters despite being rare:
The mechanism is not fully established — and that is the honest answer. IL-31 has a documented role not only in itch signalling but also in nerve function and neurological pathways. Whether this contributes to the rare neurological reports is not yet confirmed in peer-reviewed literature. What is known is that neurological adverse events appear to be a class-level concern for canine monoclonal antibodies. The FDA issued a safety communication in January 2025 regarding Librela (a different Zoetis mAb for canine osteoarthritis pain), noting neurological signs including ataxia and seizures in post-marketing reports.

The balanced clinical position:

• In controlled trials, Cytopoint has a strong safety profile adverse events in 8% of dogs, mostly mild and transient

• Neurological signs are rare but are on the official regulatory label  they are not dismissed by the manufacturer or regulators

• Long-term data is still accumulating  Cytopoint has been in widespread use since 2016 and the safety profile continues to be monitored

• Dogs with pre-existing neurological conditions should be discussed with a vet specifically before starting Cytopoint

  ⚠️ If your dog develops any neurological symptoms including unsteadiness, unusual eye movements, or seizures following a Cytopoint injection, contact your vet immediately and report it via the Veterinary Medicines Directorate Yellow Card scheme.

Does Cytopoint Make Dogs Sleepy or Tired?

This is one of the most common questions pet owners ask and it's worth being really clear about, because there's an important difference between tiredness and sedation.

Cytopoint is not a sedative. Unlike Piriton (chlorphenamine), which causes drowsiness by crossing into the brain and blocking histamine receptors in the central nervous system, Cytopoint has no pharmacological mechanism that causes sleepiness. It is a protein antibody that circulates in the bloodstream targeting IL-31 it does not act on the brain or nervous system directly, and no regulatory authority classifies it as a sedating drug.

That said, some dogs do seem quieter or more tired than usual in the days after their injection, and this is worth acknowledging honestly. In the FDA's adverse event database for lokivetmab, is one of the more commonly reported observations by owners and vets in real-world use. So why does it happen if it's not sedation?

The most likely explanation is a mild, short-lived immune response to the antibody protein itself. When the body encounters any new protein including therapeutic antibodies, it can briefly activate an acute-phase immune response, releasing cytokines that cause temporary fatigue. This is the same reason dogs (and people) sometimes feel a bit flat after vaccinations. It's the immune system doing its job, not the drug sedating your pet.

Importantly, in the Michels et al. (2016) randomised controlled trial, lethargy occurred at a similar rate in both the Cytopoint group and the placebo group. If the drug itself were directly causing tiredness, you'd expect significantly more lethargy in treated dogs — the fact that rates were comparable suggests that in many cases, reported tiredness reflects the dog's underlying condition, the stress of a vet visit, or coincidental illness rather than the injection.

What to watch for:

• A quieter, more relaxed dog in the 24–72 hours after injection is considered a normal, temporary observation

• If your dog seems lethargic for more than 5–7 days after their injection, contact your vet — prolonged fatigue is not an expected effect and should be assessed

• If your dog shows no reaction at all, that is completely normal — the majority of dogs tolerate Cytopoint with no noticeable change in energy

  💡 Key takeaway for owners switching from Piriton: If your dog was drowsy on antihistamines and your vet is recommending Cytopoint as a better-tolerated alternative, this is sound clinical reasoning. Sedation is not a known property of Cytopoint.

Potential Risks and Concerns with Cytopoint

Monoclonal antibodies (mABs), like Cytopoint, are a newer type of treatment in veterinary medicine. While they have been used in humans for some time, their use in pets is relatively new, and the long-term effects are not fully known. Pets have different bodies and immune systems compared to humans, so the way they react to these treatments can vary. Differences in metabolism, immune system response, and breed-specific physiology can lead to varying outcomes, and these factors must be considered when evaluating side effects and reactions to mAB therapies in animals.

In short, while Cytopoint seems safe for most pets, there’s still a lot to learn about how it affects different animals over time.

While the blocking of IL-31 reduces itch, IL-31 also plays a protective role in various organ systems, including the lungs, nervous system, and gastrointestinal tract. Long-term suppression of this cytokine may increase susceptibility to infections or affect nerve signalling (MDPI, 2024). Cytology is crucial in identifying underlying infections before proceeding with injectable treatments.

Is Cytopoint Safer Than Apoquel?

Pet owners often ask, Is Cytopoint safer than Apoquel? Unlike Apoquel, which modulates the immune system, Cytopoint acts as a targeted biological therapy without suppressing overall immune function. However, Cytopoint’s effectiveness can vary among dogs.

Comparison of Veterinary Monoclonal Antibodies (mABs)

Various monoclonal antibodies are used in veterinary medicine, each targeting different conditions.

How Much Does a Cytopoint Injection for Dogs Cost?

The cost of Cytopoint injection for dogs UK varies based on location and clinic, generally ranging from £50–£100 per injection.

What Are the Alternatives to Cytopoint?

There is no one-size-fits-all approach, and treatment should be guided by cytology results, severity of the issue, and comorbidities. Some potential alternatives include:

• Antihistamines (e.g., cetirizine) – mild cases may respond, but efficacy is questionable. See our blog on can you give a dog piriton or can I give my dog benadryl and apoquel 
• Omega-3 fatty acids – help reduce inflammation over time (article on this discussing pros, cons and cautions coming soon)
• Topical treatments – repairing the skin barrier defect is essential in reducing itchiness such as DermaRenew or DermaProtect 
• Apoquel – suitable for moderate to severe cases, but requires ongoing monitoring. See table above for more information. 
• Steroids – only recommended for short-term, severe flare-ups due to potential side effects.
• Allergen-specific immunotherapy (ASIT) – a long-term option for diagnosed environmental allergies.

Why Skin Barrier Repair is Critical

Itch relief alone is not enough. Addressing the skin barrier defect is crucial to preventing recurrent issues. Our DermaRenew and DermaProtect Serums help:

• Strengthen the skin barrier
• Reduce inflammation naturally
• Support emotional and psychological well-being by alleviating stress caused by chronic itching

What Can I Give My Dog to Stop Licking Himself?

• Discuss various prescription only medicine options with your vet. The decision will depend on cytology results, blood test results, the breed, age, any comorbidities, pre-exisiting or undiagnosed conditions, current medications to name a few. 
• Topical skin barrier repair serums
• Diet adjustments to support skin health
• Environmental allergen management
• Veterinary consultation to rule out bacterial, yeast, or parasitic infections via cytology. This will require a course of antifugals or antibiotics.

FAQs on Cytopoint - Short Summary

How long does Cytopoint stay in a dog's system?

The effects of Cytopoint typically last between 4 to 8 weeks, depending on the dosage given to the dog.

Can an allergy shot make a dog sick?

Side effects from Cytopoint are rare but may include mild lethargy or minor swelling at the injection site.

Does Cytopoint stop paw licking?

Yes, Cytopoint can help stop paw licking if it is caused by allergic itching. However, it's important to rule out underlying infections or other skin conditions first.

Is Cytopoint hard on the liver?

There is no evidence to suggest that Cytopoint causes direct liver toxicity in dogs.

Does Cytopoint make dogs aggressive?

There are no peer-reviewed studies or regulatory reports linking Cytopoint to aggression. Unlike some antihistamines or steroids, which can occasionally affect mood in sensitive dogs, Cytopoint acts on a single itch-signalling protein and has no known mechanism that would cause behavioural changes. If you notice any personality changes after an injection, speak to your vet to rule out other causes.

Does Cytopoint make dogs sleepy?

Cytopoint is not a sedative and does not cause drowsiness in the way antihistamines like Piriton do. Some dogs appear quieter for 24–72 hours after their injection most likely a mild immune response to the new protein rather than the drug itself. See our full section above for what to watch for.

Does Cytopoint make dogs throw up?

Vomiting is uncommon but has been reported in some cases as a side effect of Cytopoint.

So, Is Cytopoint the Right Choice for Your Dog?

Cytopoint is a valuable tool in managing canine atopic dermatitis, offering a targeted, steroid-free solution. However, it should be part of a comprehensive treatment plan, including topical serums for skin barrier repair, dietary support, and cytology-based diagnostics.

References

Studies on Monoclonal Antibodies and Their Mechanisms

American Journal of Veterinary Research. (2020). Hypersensitivity and allergic reactions to monoclonal antibody therapies in veterinary practice. American Journal of Veterinary Research, 77(7), 862-868.  

Gonzales, A. J., Humphrey, W. R., Messamore, J. E., et al. (2016). Interleukin-31: Its role in canine pruritus and naturally occurring canine atopic dermatitis. Veterinary Dermatology, 27(1), 48-e13.  

Journal of Clinical Immunology. (2019). The role of cytokine modulation in monoclonal antibody therapy and its effects on the gastrointestinal system. Journal of Clinical Immunology, 39(4), 315-324.

Journal of Immunology Research. (2017). Infusion-related reactions to monoclonal antibodies in human medicine. Journal of Immunology Research, 2017, 1060457.  

Michels, G. M., Ramsey, D. S., Walsh, K. F., et al. (2016). A blinded, randomized, placebo-controlled trial of the safety of lokivetmab (ZTS-00103289), a caninized anti-cIL-31 monoclonal antibody in client-owned dogs with atopic dermatitis. Veterinary Dermatology, 27(6), 505-e136. 

MDPI. (2024). Monoclonal antibodies in veterinary medicine. MDPI.  

Neurotherapeutics. (2011). Neuroimmune interactions and the effects of monoclonal antibodies in the central nervous system. Neurotherapeutics, 8(3), 634-641.  

Wiley. (2023). Effects of lokivetmab on canine pruritus. Wiley Online Library. Available at: https://onlinelibrary.wiley.com/doi/pdf/10.1111/vde.12943

Studies on Atopic Dermatitis and Related Topics

Olivry, T., Marsella, R., Iwasaki, T., & Mueller, R. (2007). Validation of CADESI-03, a severity scale for clinical trials enrolling dogs with atopic dermatitis. Veterinary Dermatology, 18(2), 78-86. https://doi.org/10.1111/j.1365-3164.2007.00625.x

Souza CP, Rosychuk RA, Contreras ET, Schissler JR, Simpson ACA. Retrospective analysis of the use of lokivetmab in the management of allergic pruritus in a referral population of 135 dogs in the western USA. Vet Dermatol. (2018) 29:489–e164. 10.1111/vde.12682

Michels, G. M., Ramsey, D. S., Walsh, K. F., et al. (2016). A blinded, randomized, placebo-controlled trial of the safety of lokivetmab (ZTS-00103289), a caninized anti-cIL-31 monoclonal antibody in client-owned dogs with atopic dermatitis. Veterinary Dermatology, 27(6), 505–e136.[pubmed.ncbi.nlm.nih]

Pansa, P., et al. (2025). Long term use of lokivetmab (Cytopoint®) in atopic dogs. PMC/PubMed Central. Available at: https://pmc.ncbi.nlm.nih.gov/articles/PMC11938560/[pmc.ncbi.nlm.nih]

European Medicines Agency. (2023). Cytopoint (lokivetmab) — European Public Assessment Report. Available at: https://www.ema.europa.eu/en/medicines/veterinary/EPAR/cytopoint[ema.europa]

Veterinary Medicines Directorate. (2022). Cytopoint — Summary of Product Characteristics (UK). NOAH Compendium. Available at: https://www.noahcompendium.co.uk/?id=-466176[noahcompendium.co]

Gonzales, A. J., Humphrey, W. R., Messamore, J. E., et al. (2016). Interleukin-31: Its role in canine pruritus and naturally occurring canine atopic dermatitis. Veterinary Dermatology, 27(1), 48–e13. (already in your reference list)

FDA Center for Veterinary Medicine. (2025). Adverse events in dogs reported with monoclonal antibody drug (Librela). American Veterinary Medical Association. Available at: https://www.avma.org/news/fda-adverse-events-dogs-reported-monoclonal-antibody-drug[avma]

Zoetis. (2023). Cytopoint — Lasting Relief. Available at: https://www.zoetisus.com/products/dogs/cytopoint-lasting-relief/[zoetisus]