What Are the Long-Term Side Effects of Apoquel for Dogs?

By Dr. Zubair Khalid, DVM, MS, PhD · 2026-08-14

Key Takeaways

• Apoquel (oclacitinib) functions by inhibiting Janus kinase (JAK) enzymes, which are crucial signaling proteins in immune cells, thereby suppressing the inflammatory and pruritic pathways responsible for allergic itch and atopic dermatitis. This mechanism, while effective for symptom control, also dampens certain immune responses, increasing susceptibility to infections.
• Long-term risks associated with Apoquel therapy include an increased incidence of bacterial and fungal infections (e.g., pyoderma, ear infections, demodectic mange) due to immune modulation, and potential development of skin growths such as papillomas and a possible association with certain skin cancers like mast cell tumors.
• Routine veterinary monitoring, including physical examinations and regular bloodwork (typically every six to twelve months), is essential to detect potential adverse effects such as elevated liver enzymes or altered blood cell counts (e.g., lymphopenia) that may indicate organ system impact or increased vulnerability to infection.
• Owners must maintain a diligent log of their dog's daily intake, elimination, energy levels, and any skin changes, and should never abruptly discontinue Apoquel without veterinary consultation, as this can lead to a rapid and severe rebound of pruritus and self-inflicted skin trauma.
• Immediate veterinary attention is required for signs of severe adverse reactions including difficulty breathing, collapse, seizures, or facial swelling, while new lumps, persistent ear infections, significant lethargy, or skin sores warrant a same-day veterinary appointment for prompt assessment and management.

Apoquel (generic name oclacitinib) is a common prescription medication for dogs with allergic itch and atopic dermatitis, a chronic skin condition. Most dogs tolerate it well, but long-term use does carry real risks that you should understand before continuing treatment. The most important things to know are that Apoquel does not cure allergies, it suppresses part of the immune system, and it requires regular veterinary checkups to catch problems early. If your dog has been on Apoquel for months or years, you are right to ask what could happen next.

This medication works by blocking specific proteins that drive itching and inflammation. That same action also dampens some immune responses, which is why infections and other issues can appear over time. The good news is that most side effects are manageable when caught early. The key is knowing what to watch for and keeping your veterinarian in the loop. Never stop the medication suddenly without talking to your vet, as the itch can rebound quickly and cause your dog to damage their skin.

Is This an Emergency?

Most long-term Apoquel side effects develop slowly, but a few situations require immediate care. If your dog shows any of the signs in the first row below, go to an emergency veterinary hospital now. Do not wait to call your regular clinic.

{
 "type": "triage",
 "title": "Urgency triage by severity of signs",
 "tiers": [
  {
   "tier": "danger",
   "label": "Go to emergency vet now",
   "signs": [
    "Difficulty breathing, wheezing, or rapid breathing at rest (more than 30 breaths per minute when calm)",
    "Collapse, fainting, or sudden weakness",
    "Seizures",
    "Swelling of the face, lips, or throat"
   ],
   "action": [
    "Stop giving Apoquel and transport your dog to the nearest emergency hospital immediately",
    "Call ahead if you can, but do not delay travel"
   ]
  },
  {
   "tier": "warn",
   "label": "Book a same-day appointment",
   "signs": [
    "New lumps or bumps under the skin",
    "Ear infections with discharge, odor, or head shaking",
    "Skin sores that are red, oozing, or crusty",
    "Lethargy lasting more than 24 hours"
   ],
   "action": [
    "Call your veterinarian this morning and ask for the earliest available slot",
    "Keep giving Apoquel unless your vet tells you otherwise"
   ]
  },
  {
   "tier": "safe",
   "label": "Can watch at home for a defined period",
   "signs": [
    "Mild drowsiness in the first few days after starting or increasing the dose",
    "Soft stool for one to two days without blood, vomiting, or loss of appetite",
    "Slight increase in thirst that stays stable"
   ],
   "action": [
    "Monitor for 48 hours",
    "If signs worsen, become more frequent, or do not resolve, call your vet",
    "If your dog seems painful or distressed at any point, move up the urgency level"
   ]
  }
 ]
}

What Apoquel Actually Does in the Body

Apoquel targets Janus kinase enzymes, which are signaling proteins inside immune cells. By blocking these enzymes, the drug stops the chain of events that produces itch and inflammation in the skin. This is very effective for many dogs, often within 24 hours. However, those same enzymes also help the body fight off certain infections and control cell growth. Long-term suppression of this pathway is the reason for most of the risks described below.

The medication is not a steroid, so it does not cause the classic steroid side effects like excessive thirst, panting, or muscle wasting. That is one reason vets often prefer it for long-term allergy control. But it is still an immune-modulating drug, meaning it changes how the immune system behaves. Your dog's immune system is doing less surveillance work while on this medication.

The Main Long-Term Risks

The most common long-term concerns fall into three categories: infections, skin growths, and effects on internal organs. Each has different warning signs and monitoring needs.

Infections. Because Apoquel dampens immune activity, dogs on it may develop more frequent or more severe bacterial and fungal infections. This includes skin infections (pyoderma), ear infections, and demodectic mange, a mite infestation that usually only affects dogs with weakened immunity. Watch for red, moist, or smelly skin, pustules that look like pimples, hair loss in patches, or a greasy coat. Ear infections often show up as head shaking, scratching at the ears, or a yeasty odor. If you see these signs, your vet will likely need to examine your dog and may prescribe antibiotics or antifungal medication. The infection itself is treatable, but it tells you the drug is affecting your dog's defenses.

Skin growths and masses. Some studies and clinical reports have noted that dogs on Apoquel may develop benign growths called papillomas, which are wart-like bumps caused by a virus. More concerning, there is a potential link between long-term use and certain types of skin cancer, particularly mast cell tumors. This link is not fully proven, and many dogs on Apoquel never develop any growths. But the FDA has included this as a risk to discuss with your veterinarian. The practical approach is to check your dog's skin regularly. Run your hands over their body once a week and look for any new lump, bump, or change in an existing mole or spot. Any new mass that persists for more than a few weeks should be examined by a vet, and often a fine needle aspirate, a small sample taken with a needle, can tell you what it is.

Liver and other organ effects. Apoquel is processed by the liver, and long-term use can raise liver enzyme levels on blood tests. This does not always mean the liver is damaged, but it is a sign that needs follow-up. Some dogs also develop changes in blood cell counts, particularly low white blood cells, which can make them more vulnerable to infection. Routine blood work is the only reliable way to catch these changes early. Your veterinarian should recommend a blood test every six to twelve months for dogs on long-term Apoquel. This is not optional if you want to use the drug safely.

What Else Could Be Going On

The signs above are not unique to Apoquel. Allergic skin disease itself can cause secondary infections, and older dogs naturally develop lumps and organ changes. If your dog develops a new symptom, it may be from the medication, from the underlying allergy, or from an unrelated condition. This is why you should not try to diagnose at home. A veterinary examination and possibly blood work or skin tests are needed to sort out the cause. For example, increased thirst can be a sign of kidney disease, diabetes, or Cushing's disease, all of which are common in older dogs and unrelated to Apoquel.

How to Use Apoquel Safely Long Term

The safest approach is a partnership with your veterinarian. Use the lowest effective dose, which your vet determines based on your dog's weight and response. Do not adjust the dose yourself. Many dogs can be tapered to every-other-day or twice-weekly dosing once their skin is controlled, but this must be done under veterinary guidance. Schedule a recheck appointment at least every six months, and ask for blood work at least once a year. Keep a simple log of any new symptoms, including when they started and how often they occur. This information helps your vet decide whether to continue the drug, change the dose, or switch to another treatment like allergy immunotherapy or topical therapy.

The FDA's guidance on safe use of pet medications emphasizes giving the exact dose prescribed and never sharing medication between pets. The American Veterinary Medical Association's pet owner resources also stress the importance of regular wellness visits for any dog on long-term medication. These are your best tools for catching problems before they become serious.

What You Can Do at Home Right Now

If your dog is already on Apoquel and doing well, the most useful thing you can do today is start a simple log. You do not need special equipment. A notebook or a notes app on your phone works fine.

Write down the date, the dose you give, and the time you give it. Then note three things each day: how much your dog eats, how much water they drink, and how many times they urinate. Add a line for energy level, for example "normal," "sleepy," or "slower on walks." If your dog has skin issues, describe what you see. Count the number of new hot spots, red patches, or areas of scratching in a 24 hour period. This record becomes very valuable when you talk to your veterinarian, because it turns vague worry into concrete facts.

There are two things you must not do at home. Do not change the dose on your own. Apoquel dosing is based on your dog's weight and their specific condition, and giving too much raises the risk of side effects while giving too little may not control the itch. The US Food and Drug Administration emphasizes that giving the correct amount matters for safety and effectiveness. Do not stop the medication suddenly without asking your veterinarian first. Some dogs flare badly when the drug is withdrawn, and your vet may want a tapering plan.

Do not give your dog any other medication, including over-the-counter antihistamines or supplements, without asking. Some combinations can hide symptoms or interact in ways that are hard to predict.

What to Write Down Before You Call the Vet

Before you contact your veterinarian, gather a few specific measurements. Count your dog's breathing rate at rest. Wait until they are lying down and calm, then count breaths for 30 seconds and multiply by two. A normal resting rate for most dogs is between 15 and 30 breaths per minute. If it is over 40, that is a reason to call sooner instead of later.

Check your dog's gum color. Lift the lip and look. Healthy gums are pink, like bubble gum. Pale, white, blue, or brick red gums are warning signs that need urgent attention. Press gently on the gum with your finger for two seconds, then release. The color should return within two seconds. If it takes longer, that is a sign of poor circulation.

Write down how many times your dog vomited or had diarrhea in the last 24 hours, and whether there is blood in either. Note whether your dog is drinking much more water than usual, because increased thirst can be a sign of kidney or liver issues. Also note any yellow tint to the gums, the whites of the eyes, or the skin inside the ears. Yellow color can point to liver problems.

If your dog seems painful, describe where and when. A dog that is reluctant to move, cries when picked up, or flinches when touched in a specific spot needs an examination. Do not try to diagnose this at home.

What a Veterinary Visit Usually Involves

When you bring your dog in for a long-term Apoquel check, the veterinarian will start with questions. Expect to be asked how long your dog has been on the drug, what dose, and whether you have seen any changes in appetite, thirst, urination, energy, or skin. Bring your log if you have one.

The physical exam is hands-on. The vet will feel your dog's abdomen to check organ size and look for pain. They will listen to the heart and lungs with a stethoscope. They will check the skin and ears for signs of infection. They may take your dog's temperature.

Bloodwork is common for dogs on long-term Apoquel. A typical panel checks liver enzymes, kidney values, and a complete blood count to look for anemia or changes in white blood cells. Urinalysis may be included to check for urinary tract infection. These tests are not needed at every visit, but your vet may recommend them once or twice a year.

The cost of these visits varies widely by region and clinic. A recheck exam might run from 40 to 100 dollars. Bloodwork panels often range from 100 to 250 dollars, and urinalysis adds roughly 20 to 50 dollars. These are general ranges only, not quotes. Prices depend on your location, the clinic's fee schedule, and whether any extra tests are needed. Ask your vet for an estimate before they run tests.

A Monitoring Checklist for Dogs on Long-Term Apoquel

Use this table as a simple monthly check. Print it or copy it into your notes.

When an Online Vet Can Help, and When It Cannot

Some situations in this article require hands-on care and must never be handled remotely. If your dog has pale or blue gums, difficulty breathing, collapse, seizures, repeated vomiting with blood, or is straining to urinate without producing urine, go to an emergency clinic immediately. Do not wait for a video call. A remote veterinarian cannot examine your dog's abdomen, listen to the chest, take a temperature, or run bloodwork, and those limitations matter in an emergency.

A remote consultation is genuinely useful for other situations. If your dog has been on Apoquel for months and you are wondering whether a mild increase in thirst is normal, an online vet can help you decide if a visit is needed. If your dog has a small red patch that is not spreading, a video call can let the vet see it and advise. If you have a recheck question about a known skin condition, or you want to ask about a possible medication side effect, remote care can save you a trip.

What a remote vet can do is take a thorough history, look at visible signs on video, answer questions, and in many states prescribe medication. What they cannot do is palpate the abdomen, listen to the heart and lungs, take a temperature, run bloodwork, or image anything. Prescribing rules differ by state, and a veterinarian may require an in-person examination before they will prescribe or refill Apoquel. Use remote care as a triage tool, not a replacement for physical examination when your vet recommends one.

Common Mistakes Owners Make With Long-Term Apoquel

Many owners run into trouble not because Apoquel is dangerous, but because of how it is used around other health issues. The most common mistake is stopping the medication cold turkey when the dog seems better. Apoquel controls itch, it does not cure the underlying allergy. Stopping suddenly often brings the itch back within a day or two, sometimes worse than before.

Another frequent error is assuming any new symptom is caused by Apoquel and then withholding the drug without calling your vet. A dog on long-term Apoquel can still get ear infections, hot spots, or a new lump. Blaming the medication for everything can delay treatment for a separate problem. The reverse mistake is also common: ignoring new signs like vomiting, diarrhea, or lethargy because you assume they are unrelated.

A third mistake is giving Apoquel alongside other medications without checking with your vet. Some drug combinations need adjustment. Your vet should review the full list of everything your dog takes, including supplements and flea preventives.

Finally, many owners skip routine bloodwork after the first year. Long-term use of any medication deserves periodic checks. Your vet can tell you how often your individual dog needs testing.

How to Reduce the Chance of Problems

The single best step is to use the lowest effective dose. Many dogs do well on Apoquel every other day or only during high allergy seasons. Work with your vet to find the minimum that keeps your dog comfortable. Do not adjust the dose yourself.

Keep your dog's skin and ears healthy as a second layer of defense. Regular bathing with a vet-approved shampoo removes allergens from the coat. Cleaning ears weekly can prevent infections that flare up when allergies are active. Good flea and tick control matters too, because parasite bites can trigger the same itch pathways.

Feed a consistent, high quality diet. Some dogs with food allergies improve when their diet is changed under veterinary guidance. Do not switch foods randomly, as this can make it harder to identify triggers.

Schedule a full physical exam at least once a year, and more often if your dog is older or has other conditions. The exam should include a discussion of how many days per week your dog actually needs Apoquel. Track that number between visits so you can report it accurately.

What Ongoing Management Usually Looks Like

Most dogs on long-term Apoquel live normal lives. The medication is approved for extended use, and many dogs stay on it for years without serious problems. The US Food and Drug Administration provides guidance on safe use of pet medications, including the importance of following your vet's instructions and reporting any adverse effects.

Recovery from the initial allergy flare usually takes a few days. You should see reduced scratching within 24 hours, with full effect by day three or four. Skin sores and hair loss take longer to heal, often two to four weeks. Ear infections may need separate treatment and can take a few weeks to clear.

Ongoing management is a partnership. You watch your dog daily for changes in scratching, energy, appetite, and bathroom habits. Your vet watches the bigger picture through exams and bloodwork. If bloodwork shows changes in liver or kidney values, your vet may recommend a lower dose, a drug holiday, or a switch to a different medication. These decisions are always individual.

If Apoquel is stopped for any reason, the itch usually returns within one to three days. That is expected. It does not mean the drug caused damage. It means the underlying allergy is still there.

Frequently Asked Questions

Can Apoquel cause liver damage in dogs? Liver damage is not a common reported side effect of Apoquel, but any medication can affect any organ in a specific animal. Routine bloodwork checks liver enzymes and can catch problems early. If your dog shows yellow gums, dark urine, or severe vomiting, seek emergency care. Your vet will decide whether bloodwork is needed and how often based on your dog's age, health, and other medications.

Will my dog need bloodwork forever? Not necessarily forever, but regularly. Many vets recommend bloodwork every six to twelve months for dogs on long-term Apoquel. The frequency depends on your dog's age, breed, and other health conditions. Bloodwork is quick and usually requires only a small sample. It gives your vet a baseline to compare against if problems ever arise.

Can I give Apoquel with my dog's other allergy medicine? Only if your vet approves. Some combinations are safe and even helpful, such as adding an antihistamine or a prescription diet. Other combinations can increase the risk of side effects. Always list every medication and supplement for your vet before combining anything. Never start a new drug without asking first.

What happens if I miss a dose? Give the missed dose as soon as you remember, unless it is almost time for the next dose. In that case, skip the missed dose and continue on schedule. Do not give two doses at once. A single missed dose rarely causes a serious problem. The itch may return within a day, and you can call your vet if it becomes severe.

Is Apoquel safe for a dog with cancer? This is a question only your veterinarian can answer for your specific dog. Apoquel works by suppressing part of the immune system, and your vet will weigh the benefits against any risks. If your dog has a history of cancer, your vet may recommend extra monitoring or a different medication. Be honest about your dog's full medical history.

Can I stop Apoquel if my dog seems fine in winter? Many dogs have seasonal allergies and need less medication in colder months. Talk to your vet about a trial reduction. Do not stop abruptly without guidance, as the itch can rebound. Your vet may suggest a schedule such as every other day for a week, then stopping, so you can see how your dog responds.

Related Clinical & Scientific Guides

• What Are the Side Effects of Bravecto for Dogs? What to Watch For
• Can You Give Your Dog Human Allergy Medicine? Whats Safe
• Can You Give Your Dog Dramamine for Car Sickness?

References and Further Reading

• FDA Center for Veterinary Medicine Animal Drug Information
• FDA Safe Use of Pet Medications
• AVMA Pet Owner Resources
• MSD Veterinary Manual Pet Owner Version
• AAHA Pet Owner Resources

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This article is general educational information for pet owners. It is not a substitute for veterinary diagnosis, examination, or treatment. If your pet is showing severe or rapidly worsening signs, contact an emergency veterinary hospital immediately.