Apoquel vs Cytopoint vs Zenrelia vs Numelvi: How Each Dog Itch Medicine Works and What the Labels Say

Apoquel, Zenrelia and Numelvi are prescription tablets that belong to a drug class called JAK inhibitors; Cytopoint is an injected antibody that blocks one itch signal. All four are used to control itching from allergic skin disease in dogs, but their labels differ in minimum age, warnings and how they are given. Numelvi, approved by the FDA in February 2026, is labeled for dogs from 6 months, while Apoquel and Zenrelia are labeled for dogs at least 12 months old. Which one, if any, suits your dog is a decision for your veterinarian, who knows your dog’s age, health history, vaccine schedule and other medicines.

This article explains how each product works and summarizes its official label. It does not give doses or recommend one product over another. Do not start, stop or switch any medicine without talking to your vet.

Why dogs need itch medicine in the first place

Chronic itching in dogs is most often caused by allergies: to fleas, to environmental allergens such as pollen and dust mites (atopic dermatitis), or to food ingredients. Constant scratching, licking and chewing damages the skin and invites bacterial and yeast infections. Itch medicines calm the itch and inflammation, but they do not cure the underlying allergy. Your vet will usually look for the cause too, which may include strict flea control, a food elimination trial, skin tests or allergy immunotherapy.

The four products at a glance

How JAK inhibitors work (Apoquel, Zenrelia, Numelvi)

Many of the chemical messengers that drive itch and inflammation, including interleukin-31, pass their signal into cells through enzymes called Janus kinases (JAKs). JAK inhibitors block that signaling inside the cell, which reduces itching and inflammation. Because the immune system also uses JAK pathways to fight infections and respond to vaccines, labels in this class carry infection warnings and, in some cases, vaccine warnings.

Apoquel (oclacitinib)

Apoquel was the first JAK inhibitor approved for dogs. VCA Animal Hospitals describes it as acting mainly on JAK1 and JAK3. It is approved for control of itch associated with allergic dermatitis and control of atopic dermatitis in dogs at least 12 months old, and a chewable form was approved in 2023.

Key points from the US label:

• Not for use in dogs under 12 months of age or dogs with serious infections.
• May increase susceptibility to infection, including demodectic mange, and may make existing cancers worse. New tumors, both benign and malignant, were seen in clinical studies and have been reported since approval.
• Not for use in breeding, pregnant or nursing dogs, and not evaluated in combination with steroids, cyclosporine or other systemic immune-suppressing drugs.

Read the label and safety information on Zoetis’s Apoquel page.

Zenrelia (ilunocitinib)

Zenrelia, from Elanco, was approved by the FDA in September 2024 for control of itch associated with allergic dermatitis and control of atopic dermatitis in dogs at least 12 months old.

Key points from the US label:

• Boxed warning: inadequate immune response to vaccines. The label advises stopping Zenrelia for a period before vaccination and withholding it for a period afterward, and says dogs should be up to date on vaccines before starting. Your vet will plan this around your dog’s vaccination schedule.
• In September 2025, Elanco announced that the FDA approved a label update removing earlier boxed-warning language about the risk of fatal vaccine-induced disease from modified live virus vaccines. The warning about weaker vaccine responses remains.
• Not for dogs under 12 months or with serious infections; may increase infection risk.
• Benign and malignant tumors were observed during clinical studies.
• The most common side effects listed are vomiting, diarrhea and tiredness.
• Not tested in breeding, pregnant or nursing dogs, or with steroids, cyclosporine or other immune-suppressing drugs.

Elanco publishes the full Zenrelia label.

Numelvi (atinvicitinib)

Numelvi, from Merck Animal Health, was approved by the FDA in February 2026 for control of itch associated with allergic dermatitis in dogs 6 months and older. Merck describes it as a second-generation JAK inhibitor that is more selective for JAK1 than for other JAK enzymes. It has also been authorized in the UK.

Key points from Merck’s safety information:

• Not for use in dogs under 6 months of age or dogs with serious infections.
• May increase susceptibility to opportunistic infections, including demodectic mange and interdigital furunculosis (painful bumps between the toes).
• New benign and malignant tumors have been reported in dogs treated with other JAK inhibitors.
• Effectiveness and safety have not been evaluated in a field study beyond 28 days.
• Safe use has not been evaluated in breeding, pregnant or nursing dogs, or with steroids, cyclosporine or other immune-suppressing drugs.
• Merck states there is no need to adjust vaccination schedules.

See Merck’s Numelvi page for the full prescribing information.

How Cytopoint works

Cytopoint (lokivetmab) is a monoclonal antibody, a lab-made protein designed for dogs that binds to and neutralizes interleukin-31, one of the main signals that tells the nervous system “itch.” Because it targets one messenger outside the cells rather than blocking broader immune signaling, it works differently from the JAK tablets. It is given as an injection at the vet clinic, and VCA notes that one injection typically lasts at least four to eight weeks.

Cytopoint is licensed in the US by the USDA (as a biologic) rather than approved by the FDA. It is labeled for atopic dermatitis and allergic dermatitis in dogs. It does not carry the 12-month minimum age found on Apoquel and Zenrelia; in the EU and UK it is authorized for dogs of any age weighing at least 3 kg. According to VCA, possible side effects include sleepiness, vomiting, diarrhea, reduced appetite and pain at the injection site, and allergic reactions are rare. Safety in pregnant or nursing dogs has not been established. It does not help every dog; some respond better than others. Product information is on Zoetis’s Cytopoint page.

What your vet will weigh

• Health history. Past or current infections, demodectic mange, tumors or other illnesses matter, especially for JAK inhibitors.
• Vaccines. Timing matters most for Zenrelia, per its boxed warning.
• Other medicines. Including steroids and cyclosporine.
• Practicalities. A daily tablet at home versus periodic clinic injections, and whether your dog takes pills easily.
• Cost. Prices vary by your dog’s weight, the product, the clinic and how often treatment is needed. Ask for an estimate; some pet insurance plans help with ongoing allergy care.

Questions to ask your vet

1. What is likely causing the itch, and how will we look for the cause?
2. Which options suit my dog’s age and health?
3. What side effects should I watch for at home?
4. How does this treatment fit with my dog’s vaccines and other medicines?
5. What monitoring will my dog need, and how often?
6. What will treatment cost per month, and are there alternatives if it does not work?

Call your vet promptly if your dog

• Develops a new lump, bump or skin mass
• Has a fever, cough, lethargy or other signs of infection
• Has repeated vomiting, diarrhea or stops eating
• Develops facial swelling, hives, trouble breathing or collapses after a treatment (an emergency)
• Gets red, painful bumps between the toes or patchy hair loss
• Is still very itchy or the skin is getting worse

Bottom line

Apoquel, Zenrelia and Numelvi are daily JAK-inhibitor tablets with labels that warn about infections and tumors; Zenrelia also has a boxed warning about vaccine response, and Numelvi is labeled for younger dogs, from 6 months. Cytopoint is an antibody injection that blocks the IL-31 itch signal and lasts for weeks. None cures allergies. Read the official labels, write down your questions, and let your veterinarian decide which option, if any, is right for your dog.

FAQ

Which is safest: Apoquel, Cytopoint, Zenrelia or Numelvi?

There is no single answer for every dog. Each has its own label warnings and approved ages. Your vet weighs these against your dog’s health history, age and other medicines.

Can a puppy take these itch medicines?

Apoquel and Zenrelia are labeled only for dogs at least 12 months old. Numelvi is labeled for dogs from 6 months. Cytopoint does not have the same 12-month restriction. Ask your vet what is appropriate for a young dog.

Do these medicines cure allergies?

No. They control itching and inflammation. Managing the cause, such as fleas, food or environmental allergens, is usually part of long-term care.