I watched this conversation play out hundreds of times at the front desk in Albany. The DVM would come out after a skin consult, hand the family a discharge sheet, and say something like “we could try Apoquel, or we could go with Cytopoint.” The family would nod, walk to the car, and Google both from the parking lot.
That was 2017. Today the conversation has two more names in it: Zenrelia and Numelvi. Four medications, three mechanisms, and the same family in the same parking lot trying to sort them out.
Four medications, three mechanisms
All four medications control allergic itch, but they reach the itch signal through different doors.
Apoquel (oclacitinib) is a JAK inhibitor, meaning it blocks Janus kinase enzymes that carry the itch signal from the immune system to the skin. Specifically, it targets JAK1. The itch stops fast, usually within four hours. The tradeoff: JAK1 does more than carry itch signals. It's involved in immune surveillance, so blocking it can increase susceptibility to skin infections and, in some dogs, allow subclinical masses to surface. Apoquel has been on the market since 2014, and a ten-year post-market review in JAVMA showed no new safety signals over a decade of widespread use. That's the longest real-world dataset any of these drugs has. Given as a daily tablet. Approximate cost: $60 to $120 per month depending on your dog's weight.
Zenrelia (ilunocitinib) is also a JAK inhibitor, but it was designed for more selective targeting than Apoquel. The clinical pitch is the same itch control with less off-target immune suppression. Early clinical data is encouraging, and the switch conversation usually starts when a dog on Apoquel shows declining neutrophil counts or increasing infection frequency. The limitation is time: Zenrelia doesn't have Apoquel's decade of post-market surveillance data yet. Given as a daily tablet. Pricing is comparable to Apoquel at most clinics.
Cytopoint (lokivetmab) works through a completely different mechanism. It's a monoclonal antibody that targets interleukin-31 (IL-31), one specific cytokine that triggers allergic itch. Because it doesn't suppress the broader JAK pathway, there are fewer reports of immune-related side effects in practice. Given as an injection at the clinic every four to eight weeks. Approximate cost: $50 to $150 per injection depending on dog size. The tradeoff: not every dog responds fully, the effect can fade before the next injection is due, and if your dog's itch involves more than IL-31, Cytopoint alone won't cover it.
Numelvi, marketed by Merck, is the newest entrant. It combines an isoxazoline compound with a topical corticosteroid in an oral formulation. Different mechanism from both JAK inhibitors and Cytopoint. Merck is marketing it aggressively through vet clinics, and you may see it mentioned on your clinic's social media or in the exam room. The real-world safety dataset is the smallest of the four. Given as a daily tablet. Pricing varies by clinic. If your vet suggests it, ask how it compares to the options your dog has already tried.
Which medication for which situation
There's no single best allergy drug. There's the one that fits your dog's pattern, your dog's bloodwork, and your budget. Here's how most veterinary dermatologists I worked with at Angell would frame the decision.
First-time allergies, mild to moderate itch: Cytopoint is often the first try. One injection, no daily pills, no systemic immune suppression. If it controls the itch for four to six weeks, you have a simple protocol. If it fades at two weeks or doesn't touch the itch at all, a JAK inhibitor is the next conversation.
Chronic or severe atopic dermatitis: Apoquel or Zenrelia as daily oral maintenance. The itch is driven by multiple pathways, and JAK inhibition covers more of them than a single-cytokine antibody. Apoquel has the longer track record. Zenrelia is the option when Apoquel's side-effect profile (infections, bloodwork shifts) is becoming a problem.
Dogs who've been on Apoquel and it's not holding: Two paths. If the itch control is good but the bloodwork is concerning (neutrophil decline, liver enzyme elevation), Zenrelia is the lateral move: same drug class, different selectivity profile. If Apoquel is losing effectiveness against the itch itself, Cytopoint can be added alongside it, because they work through different mechanisms and can be used together.
Injection-phobic dogs or owners: Apoquel, Zenrelia, or Numelvi are all oral tablets. Cytopoint requires a clinic visit for each injection.
Cost pressure: Do the monthly math. Apoquel at $2 to $4 per day runs $60 to $120 per month. Cytopoint at $50 to $150 every four to eight weeks can be cheaper for large dogs who hold the full duration, or more expensive for small dogs who need it every four weeks. Zenrelia pricing is comparable to Apoquel. Ask your clinic for the monthly number, not the per-dose number.
Breed-specific patterns worth knowing
Allergy medications aren't dosed by breed, but certain breeds show patterns that shape how the conversation goes. Plumb's Veterinary Drug Handbook, the reference most US vets keep on their desk, lists weight-based dosing for both oclacitinib and ilunocitinib. The breed patterns below affect which drug your vet reaches for, not how much.
French Bulldogs and English Bulldogs come with BOAS (brachycephalic obstructive airway syndrome, the breathing-structure issue that makes the face flat) and tend toward complex skin. Some owners report Apoquel making skin issues worse rather than better. These breeds often end up on combination protocols or rotating between Cytopoint and a JAK inhibitor seasonally.
Labrador Retrievers on long-term JAK inhibitors need liver and kidney monitoring on schedule. Labs are predisposed to weight gain and metabolic conditions, and adding immune modulation to that picture means the bloodwork panel every six months isn't optional.
West Highland White Terriers are the breed most dermatologists will tell you often needs combination therapy. Single-drug control of Westie skin disease is the exception, not the rule.
Cocker Spaniels with seasonal allergies sometimes land on a protocol that combines monthly Cytopoint injections from May through September with Apoquel for breakthrough itch, then nothing through winter. That seasonal approach reduces total drug exposure over the dog's lifetime.
Weimaraners can develop allergic dermatitis that moves fast. Open wounds within two weeks of a flare, even on Apoquel, is a pattern dermatologists see in this breed. If your Weimaraner is breaking through medication, don't wait for the recheck. Call the clinic.
What to track on any allergy medication
Whichever drug your vet chose, five things are worth logging between visits. This isn't busywork. It's what your vet actually reads at the recheck, and without it the conversation defaults to “seems better” or “I think it's getting worse,” neither of which gives the clinic enough to adjust the protocol.
First: symptom frequency and severity. How many times per day is the dog scratching, licking paws, or rubbing its face? A number beats an adjective. “Scratched six times today” tells the DVM more than “still itchy.”
Second: medication response time. After each dose or injection, how many hours until the scratching slows? If Cytopoint used to last six weeks and now fades at three, that's a pattern. If Apoquel used to quiet the itch within four hours and now takes twelve, that's worth noting.
Third: new lumps, skin infections, or GI changes. Any new lump on a dog taking a JAK inhibitor gets aspirated at the clinic. Recurring ear infections or hot spots suggest the immune suppression cost is adding up. Persistent soft stool or vomiting after the initial settling period deserves a call.
Fourth: seasonal pattern. Does the itch start in April and end in October? Or is it year-round? This distinction determines whether your dog needs seasonal or maintenance dosing and whether immunotherapy (allergy testing and desensitization) is worth pursuing.
Fifth: bloodwork schedule. For JAK inhibitors, a CBC (the red-and-white-cell count panel) before starting, again at three to six months, and then at least annually. The specific line to watch: neutrophils. A chemistry panel checking liver and kidney values gets added for senior dogs. The medication side-effect tracking page walks through how to keep these records organized between rechecks.
When medication alone isn't enough
Some dogs go through Apoquel, Cytopoint, and Zenrelia and still scratch. That's the point where the conversation shifts to immunotherapy: intradermal allergy testing (injections under the skin that map exactly what the dog reacts to) followed by desensitization shots or sublingual drops tailored to those specific allergens.
Immunotherapy isn't fast. Most protocols take six to twelve months to show results, and success rates run around 60 to 80 percent in published studies. It's also the only approach that tries to retrain the immune response rather than block it. The Merck Veterinary Manual, the reference textbook clinicians use, calls allergen-specific immunotherapy the only treatment that can alter the underlying disease process in canine atopic dermatitis. That's the chapter I used to photocopy for the front desk when an owner asked why allergy shots take so long.
While immunotherapy ramps up, most dogs stay on a JAK inhibitor or Cytopoint for symptom control. The medications and immunotherapy aren't competitors. They're layers.
The conversation to have with your vet
Don't walk in asking for a specific drug by name. Walk in with your dog's pattern: when the itch started, what makes it worse, whether it's seasonal or year-round, what's been tried and how long it held. That gives the DVM enough to match the mechanism to the problem.
Three questions worth asking: What mechanism does this medication use, and why does it fit my dog's allergy pattern? What should I watch for between rechecks? And what does the monthly cost look like at my dog's weight?
The Apoquel deep-dive covers the side-effect profile, long-term safety data, and monitoring protocol for that specific drug. If your vet has already chosen Apoquel and you want to know what the ten-year data says, start there.
Questions about dog allergy medications
Can my dog switch from Apoquel to Zenrelia?
Yes. Both are JAK inhibitors given as daily tablets, and most vets can switch directly without a washout period. The usual reason to switch is bloodwork changes on Apoquel (declining neutrophils, rising liver enzymes) or persistent infections. Zenrelia targets the JAK pathway more selectively, so the hope is fewer off-target immune effects. Your vet will set the Zenrelia dose based on your dog's weight and recheck bloodwork at four to six weeks to confirm the new drug is holding.
Why does Cytopoint stop working after a few weeks for some dogs?
Cytopoint is a monoclonal antibody that neutralizes interleukin-31, one specific itch cytokine. Some dogs have allergic itch driven primarily by IL-31, and Cytopoint controls them completely for four to eight weeks. Other dogs have significant itch from pathways Cytopoint doesn't touch. When it fades early, it's usually because IL-31 isn't the only driver. That's the conversation where Apoquel or Zenrelia comes up, because JAK inhibitors block a broader set of signals.
Is Numelvi the same as Apoquel?
No. Numelvi (lotilaner plus mometasone, marketed by Merck) is a different drug with a different mechanism. It combines an isoxazoline compound with a topical corticosteroid in an oral formulation. It's newer to market and the long-term safety dataset is smaller than Apoquel's decade of post-market surveillance. Your vet can explain how Numelvi fits relative to JAK inhibitors and Cytopoint based on your dog's allergy pattern.
How much does each allergy medication cost per month?
Approximate ranges in the US as of early 2026: Apoquel runs $2 to $4 per day depending on the dog's weight (roughly $60 to $120 per month). Cytopoint injections cost $50 to $150 per dose at the clinic, given every four to eight weeks. Zenrelia pricing is comparable to Apoquel at most clinics. Numelvi pricing varies by clinic. These are ballpark figures. Your clinic's pricing depends on supplier contracts and your dog's weight class. Ask the front desk for the monthly cost before starting.
Do any of these medications cure allergies, or is my dog on them for life?
None of them cure the underlying allergy. They control the itch signal while the drug is active. Dogs with seasonal allergies may only need medication during pollen months. Dogs with year-round atopic dermatitis, food allergies, or dust mite sensitivity typically need ongoing treatment. Immunotherapy (allergy shots or sublingual drops based on intradermal testing) is the only approach that attempts to retrain the immune system. It works for some dogs and takes six to twelve months to show results. Your vet or a veterinary dermatologist can discuss whether immunotherapy makes sense alongside or instead of medication.
What bloodwork should my vet run while my dog is on allergy medication?
For Apoquel and Zenrelia (JAK inhibitors): a CBC, which is the red-and-white-cell count panel, before starting and at three to six months. Neutrophils are the line to watch. A chemistry panel checking liver and kidney values is usually added for older dogs or dogs on multiple medications. For Cytopoint: no routine bloodwork is standard because it doesn't suppress the broader immune system. Your vet may still run baseline labs annually. For any long-term medication, annual bloodwork is the minimum. Twice a year is better for senior dogs.
Four drugs. Three mechanisms. The right one depends on your dog's itch pattern, bloodwork, breed history, and budget. Track what changes between rechecks, bring the log to the clinic, and let your vet adjust the protocol with actual data instead of a guess. If the current medication isn't holding, that's a phone call, not a dose change at home.
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Rachel Howland, CVT (ret.), spent a decade in clinic: seven years in a mixed practice in upstate New York, then three on the internal-medicine floor at Angell Animal Medical Center in Boston. She left practice in 2017 and has written about small-animal health since. She does not diagnose or prescribe; she explains what your vet's records are telling you and what questions are fair to ask.