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Cats | C. "A cat is not a small dog" — species specificity (this section is the top priority of this tier; read it before moving on)

Applying dog knowledge to cats is the deadliest beginner mistake. This chapter breaks down four differences that cannot be transplanted: as an obligate carnivore, the cat must get taurine, arginine, vitamin A, and arachidonic acid from meat; an innate deficit in hepatic glucuronidation turns human painkillers, essential oils, and canine flea spot-ons into poisons; a cat in pain does not vocalize or limp; and stress itself is a disease-causing factor. A dog-versus-cat quick-reference table is included for checking the medicines, cleaners, and feeding practices in your home.

Cats | C. "A cat is not a small dog" — species specificity (this section is the top priority of this tier; read it before moving on)

This chapter is compiled from the cat section of the veterinary animal encyclopedia. The same sign is handled differently in different species, and copying what is done for another species can do harm — confirm which animal you are dealing with first.

The deadliest mistake owners and beginners make is applying dog knowledge to cats. Four differences that cannot be transplanted:

C-1 Metabolism: the cat is an obligate carnivore

DifferenceThe reality in catsDogs can, cats cannotDirect consequence for the owner
TaurineSynthetic capacity is insufficient; it must come from foodDogs can synthesize enough on their ownLong-term dog food or home-made meat diets → dilated cardiomyopathy (DCM) plus feline central retinal degeneration leading to blindness
ArginineHigh requirement; deficiency stalls the urea cycleDogs are more tolerantDeficiency can cause acute hyperammonemia and neurological signs
Vitamin ACan use only preformed vitamin ADogs can convert β-carotene into vitamin AVegan cat food = physiologically unworkable; yet overfeeding liver causes vitamin A toxicity (skeletal lesions)
Arachidonic acidCannot convert enough from linoleic acidDogs can convert itHome-made meals based on plant oils do not qualify
NiacinLow efficiency of conversion from tryptophanDogs convert efficientlySame as above
Carbohydrate metabolismLow hepatic glucokinase activity; poor tolerance of high-carbohydrate dietsDogs tolerate them betterHigh-carbohydrate dry food plus obesity is the main driver of feline diabetes
Fasting toleranceExtremely poor. Negative energy balance rapidly packs fat into the liverDogs can hold out longer"Not eating — watch it for a few days first" = hepatic lipidosis; rapid crash dieting for weight loss triggers it just the same
Thirst driveInnately low; ancestors took their water from preyDogs drink enough on their ownDry food only plus a single water bowl → chronic mild dehydration → burden on the lower urinary tract and kidneys

C-2 Hepatic detoxification: an innate deficit in glucuronidation

Part of the feline UDP-glucuronosyltransferase (UGT) family has lost gene function, so a large number of compounds that "humans and dogs can metabolize safely" are cleared extremely slowly in the cat's body. This is the root mechanism behind feline poisoning cases.

Substance classWhy it is especially lethal to catsOwner action
Acetaminophen / paracetamolCannot be effectively glucuronidated → toxic metabolites accumulate → hemoglobin oxidation (Heinz bodies), methemoglobinemia (mucous membranes turn brown / swelling of the face and paws), liver necrosis. A very small amount can be lethalLock up every painkiller anyone in the household uses; if ingestion is suspected, do not wait for signs — go to the veterinarian immediately
NSAIDs (human ibuprofen / naproxen / aspirin, etc.)Half-lives are markedly prolonged in cats; renal and gastrointestinal mucosal toxicity is amplifiedFeline pain relief only by veterinary prescription; human and dog medications must not be repurposed
Phenol / cresol cleaners, essential oils (tea tree, eucalyptus, citrus, pine, peppermint, wintergreen)The same metabolic bottleneck; cats also groom residues off the floor or their skin and swallow them; diffusers make cats inhale passivelyNo phenolic cleaners or essential-oil diffusion in a cat household; floors must dry completely after use
Benzoates, propylene glycolRed blood cells readily form Heinz bodies (feline hemoglobin carries more sulfhydryl groups)Check cat-food labels
Allium species (onion, garlic, chives, scallion)Oxidative hemolysisGive no human food containing onion or garlic
Canine synthetic pyrethroid (permethrin) spot-onsCats cannot metabolize it → whole-body tremors, seizures, deathCanine topical flea products must not be used on cats under any circumstances; in a household that also has a dog, a freshly treated dog must be separated from the cats until dry (【no single authoritative value for this item: the whitelisted sources give no cat-specific reference value for separation hours; the Merck Veterinary Manual entry "Plant-Derived Insecticide Toxicosis" states that "cats appear to be more sensitive to pyrethroid toxicity" but gives no separation hours, 2026-07-30】; as a rule, lift the separation only once the topical product is completely dry and the cats cannot contact the dog's fur by grooming)
Human topical skin medications (5-fluorouracil (5-FU) cream, estrogen gels / patches, calcipotriene, steroid-containing ointments)Licking or rubbing against them poisons the cat; 5-FU is extremely lethal to catsCover medicated skin; do not let the cat touch it or share the bed

C-3 Pain is concealed (a cat will not tell you it hurts)

Cats are prey animals; showing weakness means death. A cat in pain usually does not vocalize, limp, or whine.

What pain looks like in a dogWhat pain looks like in a cat (owners most often misread it as "getting old / turning quiet")
Whining, obvious limpingNo longer jumps onto the windowsill or sofa (switches to stair-step routes)
Licks the sore spot, seeks comfortHides under the bed or in the wardrobe and does not come out to socialize
Clearly reduced appetiteEats slowly, leaves half, or eats only soft food (oral pain)
Resists touch and barksWalks away when touched, or suddenly bites (petting-induced aggression)
Grooms less (mats, dander) or over-grooms one spot only (that spot hurts)
Posture: head-down crouch, ears rotated outward and pressed down, half-closed eyelids, whiskers pulled back
Eliminates outside the litter box (cannot step over the rim; squatting hurts)

Clinically, structured scoring can be used (such as the Feline Grimace Scale——✅existence verified: Evangelista MC, Watanabe R, Leung VSY, et al. "Facial expressions of pain in cats: the development and validation of a Feline Grimace Scale." *Scientific Reports* 2019;PMID 31836868;,;more practical on the owner's side is a list of "things it used to do and no longer does" — write down 5 things it loves to do and record month by month how many it can still do.

C-4 Stress in cats is a "disease-causing factor," not just an "emotional issue"

Concrete disease / misjudgment triggered by stressMechanism / presentation
Feline idiopathic cystitis (FIC) and feline lower urinary tract disease (FLUTD)Stress is a core trigger; in male cats it can worsen into urethral obstruction = an hours-scale lethal emergency
Recurring upper-respiratory signsFeline herpesvirus-1 (FHV-1) lies latent in ganglia and reactivates under stress → sneezing, painful eyes
Over-grooming hair loss, picaBehavioral; often mistakenly treated as a skin disease alone
Aggression, urinating around the home / sprayingMostly resource competition and environmental problems, not the cat being "bad"
Stress hyperglycemiaBlood glucose drawn at the hospital spikes → a single high glucose reading cannot diagnose diabetes; it must be read together with fructosamine / home monitoring
The hospital effectHeart rate, respiration, and blood pressure in the exam room are all pushed up by stress → before blood pressure is measured the cat must first be allowed to settle, and measurement should take place in a quiet room (✅existence verified: the 2018 ACVIM hypertension consensus statement reads "the patient...should be allowed to acclimate to the measurement room for 5-10 minutes before BP measurement is attempted" and "The environment should be isolated, quiet, and away from other animals",,

→ Direct corollary: "Cat-friendly care" is not a service add-on; it is the precondition for diagnostic accuracy and treatment success. Carrier desensitization training, carriers with removable tops, towel covering, and waiting areas separated from dogs are all part of the quality of medical care.

C-5 Other dog-cat differences that often get transposed (quick reference)

ItemDogCat
ThyroidMainly underactiveMainly overactive (hyperthyroidism), common in older cats
Main type of heart diseaseAcquired mitral valve degeneration, DCM; coughing is commonHypertrophic cardiomyopathy (HCM); feline heart disease usually does not cough, and often debuts as acute rapid breathing or hind-limb paralysis (aortic thromboembolism)
Kidney diseaseSigns become obvious relatively earlyExtremely concealed; weight quietly drops, and drinking and urinating more are often written off as "aging"
ArthritisObvious limpingAlmost no limping; shows only as "stopped jumping" and has long been severely underestimated
Lymphoma / intestinal diseaseThe line between chronic enteropathy and small-cell lymphoma is blurred; simultaneous inflammation of "pancreas + biliary tract-liver + intestine" (triaditis) is a cat-specific combination
Mammary tumorsHigher proportion benignHigh proportion malignant; any mammary lump should be checked as early as possible
AnesthesiaSensitive larynx prone to laryngospasm; small body size leaves low tolerance for error in temperature and fluid volumes

Limits of this content

The content of this chapter comes from the cat section of the veterinary encyclopedia (the original location and the content hash are recorded in the evidence chain). The sources listed at the end are the authoritative materials cited by that section; the correspondence is chapter-level, which does not mean that every sentence is traced sentence by sentence to a given source. This material is for education and cannot replace diagnosis and prescription by a licensed veterinarian; in an emergency seek care immediately. It has not been clinically reviewed by a named veterinarian.

FAQ

Why are human painkillers especially dangerous to cats?
Part of the feline UDP-glucuronosyltransferase family has lost gene function, so acetaminophen cannot be effectively glucuronidated; the toxic metabolites that accumulate cause hemoglobin oxidation, methemoglobinemia, and liver necrosis, and a very small amount can be lethal. Human and dog medications must not be repurposed — feline pain relief only by veterinary prescription.
ヒト用鎮痛薬はなぜ猫に特に危険なのですか?猫の UDP-グルクロン酸転移酵素ファミリーは一部の遺伝子機能を欠いており、アセトアミノフェンをグルクロン酸抱合で有効に処理できません。毒性代謝物が蓄積するとヘモグロビン酸化、メトヘモグロビン血症、肝壊死を起こし、ごく少量でも致死的になり得ます。ヒト用薬・犬用薬の流用は一切不可で、猫の鎮痛は獣医師の処方のみです。
Why are human painkillers especially dangerous to cats?Part of the feline UDP-glucuronosyltransferase family has lost gene function, so acetaminophen cannot be effectively glucuronidated; the toxic metabolites that accumulate cause hemoglobin oxidation, methemoglobinemia, and liver necrosis, and a very small amount can be lethal. Human and dog medications must not be repurposed — feline pain relief only by veterinary prescription.
How does a cat show that it is in pain?
Cats are prey animals and showing weakness means death, so a cat in pain usually does not vocalize, limp, or whine. Common signs are no longer jumping onto the windowsill, hiding under the bed, eating slowly or eating only soft food, walking away when touched, grooming less or over-grooming one spot only, plus a head-down crouch, ears rotated outward and pressed down, and eliminating outside the litter box. Owners can keep a list of "things it used to do and no longer does" and record it month by month.
猫は痛いときにどんな様子を見せますか?猫は被捕食者で、弱みを見せることは死を意味するため、痛くても普通は鳴かず、跛行せず、うめきません。よくある表れは、窓台に跳び乗らなくなる、ベッドの下に隠れる、食べるのが遅い・柔らかい物しか食べない、触ると離れる・突然咬む、毛づくろいが減る/一箇所だけ過剰にする、頭を下げてうずくまる、耳が外向きに倒れる、トイレの外での排泄などです。飼い主は「以前はしていたのに今はしない事」のリストを毎月記録するとよいでしょう。
How does a cat show that it is in pain?Cats are prey animals and showing weakness means death, so a cat in pain usually does not vocalize, limp, or whine. Common signs are no longer jumping onto the windowsill, hiding under the bed, eating slowly or eating only soft food, walking away when touched, grooming less or over-grooming one spot only, plus a head-down crouch, ears rotated outward and pressed down, and eliminating outside the litter box. Owners can keep a list of "things it used to do and no longer does" and record it month by month.
We keep a dog and a cat at home — can they share a flea spot-on?
No. Cats cannot metabolize canine synthetic pyrethroid (permethrin) spot-ons, which cause whole-body tremors, seizures, and death. In a household that also has a dog, a freshly treated dog must be separated from the cats, and as a rule the separation is lifted only once the topical product is completely dry and the cats cannot contact the dog's fur by grooming.
犬と猫を一緒に飼っています。ノミ駆除のスポット剤は共用できますか?できません。犬用合成ピレスロイド permethrin スポット剤を猫は代謝できず、全身の震え、けいれん、死亡を起こします。犬猫同居の家庭では、薬を付けたばかりの犬を猫と隔離し、原則として外用薬が完全に乾き、猫が毛づくろいで犬の毛に触れない状態になってから隔離を解除してください。
We keep a dog and a cat at home — can they share a flea spot-on?No. Cats cannot metabolize canine synthetic pyrethroid (permethrin) spot-ons, which cause whole-body tremors, seizures, and death. In a household that also has a dog, a freshly treated dog must be separated from the cats, and as a rule the separation is lifted only once the topical product is completely dry and the cats cannot contact the dog's fur by grooming.

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獸醫百科編輯部・《Cats | C. "A cat is not a small dog" — species specificity (this section is the top priority of this tier; read it before moving on)》・IDAEO 知識庫・2026-08-13・https://km.idaeo.ai/post/vet/cats-are-not-small-dogs

Updated 2026-08-14

更新 2026-08-14T04:47:48.739Z · server-rendered · four-language · IDAEO 知識庫