Common toxic foods for dogs — reference guide

Chocolate

Toxic compound: methylxanthines (theobromine + caffeine). Toxic dose: ~20 mg/kg theobromine for mild signs, 40+ mg/kg for severe. Concentration varies wildly by chocolate type: white chocolate ~0.25 mg/g, milk chocolate ~2 mg/g, dark ~5-8 mg/g, baker's ~14-16 mg/g, cocoa powder ~20-26 mg/g.

Symptoms 2-4h: vomiting, restlessness, excessive thirst. 6-12h: cardiac (tachycardia, arrhythmia), neurological (tremors, seizures).

→ Use the chocolate toxicity calculator to compute the exact dose for your dog's weight + the type and amount eaten.

Xylitol (sugar-free sweetener)

Found in: sugar-free gum, "no sugar added" baked goods, some peanut butters, mints, mouthwash, toothpaste. Dramatic toxicity — 100 mg/kg causes hypoglycaemic shock, 500 mg/kg causes liver failure. A single piece of 5-gram xylitol gum (typical: 0.3-1 g xylitol per piece) is dangerous for a 5 kg dog.

Symptoms within 30-60 min: vomiting, weakness, loss of coordination, seizures. Hypoglycaemia is rapid. This is the fastest-acting common dog toxin — get to a vet immediately.

→ Xylitol toxicity calculator

Grapes + raisins

Toxic compound: unknown (tartaric acid is the leading hypothesis). Cause acute kidney injury. There is no reliable threshold dose — some dogs develop kidney failure from 1-2 grapes; others tolerate handfuls. The unpredictability is exactly what makes them dangerous: treat every ingestion as if it's the highest-risk case.

Raisins are ~4-5× more concentrated than grapes (water removed) and cause kidney injury at lower fresh-weight thresholds.

Symptoms 6-12h: vomiting, lethargy, anorexia. 24-72h: kidney injury appears in bloodwork (creatinine rises).

→ Grape calculator · → Raisin calculator

Onion + garlic (Allium family)

Toxic compounds: thiosulphates (n-propyl disulphide is the principal one). Damage red blood cells, causing haemolytic anaemia. Toxic dose: ~5 g/kg for onion (so ~100 g — about one medium onion — for a 20 kg dog). Garlic is ~5× more potent — toxic at ~1 g/kg.

Powdered forms are dramatically more concentrated than fresh — a teaspoon of garlic powder can equal a head of fresh garlic by toxic dose. Cooking does NOT destroy the toxin.

Symptoms 24-72h (delayed onset): pale gums, lethargy, weakness, exercise intolerance. Severe cases need blood transfusion.

Foods to watch: holiday stuffing, onion soup mix, garlic-marinated meat, baby food (often contains onion powder), garlic supplements marketed for dogs (no evidence they help; some risk).

Macadamia nuts

Toxic mechanism: unknown. Specifically affects dogs (humans + most other species unaffected). Toxic dose: ~2 g/kg — about 16 nuts for a 20 kg dog.

Symptoms 12-24h: weakness in hind legs, tremors, vomiting, hyperthermia. Resolution usually within 24-48 hours with supportive care; rarely fatal but profoundly uncomfortable for the dog.

High-risk scenarios: chocolate-covered macadamia (double toxin + the combination stresses the cardiovascular system more than either alone).

Avocado

Toxic compound: persin. Mildly toxic for dogs (much more toxic for birds, rabbits, and horses). The pulp + flesh cause GI upset; the pit is a foreign-body obstruction risk + contains higher persin concentration.

Toxic dose: not well-defined. Most dogs handle a small bite of guacamole without issue; significant ingestion or eating the pit/skin can cause vomiting + diarrhoea + (rarely) pancreatitis from the fat content. Bigger concern is the pit — surgical removal in the worst case.

Alcohol + caffeine

Alcohol toxic dose: 5 ml/kg of 40% spirits causes CNS depression; 10 ml/kg can be fatal. Also: bread dough (active yeast generates ethanol in the warm stomach), some sweetened cocktails (xylitol or chocolate also present), beer-soaked food.

Caffeine toxic dose: similar mechanism to chocolate (it's a methylxanthine). 30 mg/kg causes mild signs, 100+ mg/kg severe. A 200mg caffeine pill (one OTC alertness tab) is dangerous for a 5 kg dog. Coffee grounds, espresso, energy drinks all in scope.

Ibuprofen, aspirin, acetaminophen (Tylenol)

Single-dose toxicity is severe. Never give human pain meds to a dog without explicit vet guidance.

• Ibuprofen (Advil, Motrin): 50 mg/kg → GI ulceration; 100 mg/kg → acute kidney injury; 250 mg/kg → seizures. One 200mg tab is dangerous for a 5 kg dog.
• Naproxen (Aleve): Even worse — 5 mg/kg already toxic. Half-life 35-72 hours in dogs.
• Acetaminophen (Tylenol): 75 mg/kg → liver injury; 100+ mg/kg → severe liver failure. Especially dangerous because cats are dramatically more sensitive (lethal at 10 mg/kg) — never use in cat households.
• Aspirin: Less acutely toxic but still causes GI ulceration at higher doses. Vet-prescribed buffered aspirin is sometimes used short-term, but never give the human-formulated tablet without dosing guidance.

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Frequently asked questions

My dog ate one piece of [X]. Do I need to call the vet?

Depends on what X is and how much. The reference above lists the toxic threshold for each food in mg/kg of body weight. For a 20 kg dog, a single grape can be enough to cause kidney injury; a single bite of milk chocolate is usually fine. Always call when in doubt — Pet Poison Helpline (855-764-7661) and ASPCA (888-426-4435) are 24/7 and triage for the cost of a consultation fee.

Is garlic powder or onion powder more dangerous than fresh?

Yes, dramatically. Dehydrated/powdered alliums are 5-10× more concentrated by weight than the fresh form. A teaspoon of onion powder can equal half a fresh onion in toxic dose. This is why seasoned table scraps (especially from holiday meals) cause more emergency visits than pets eating the raw vegetable.

What about cooked vs raw onion/garlic?

Cooking does NOT destroy the toxic compounds (n-propyl disulfide, thiosulphate). Cooked onions in stuffing, garlic in pasta sauce, onion soup mix on roasted meat — all still toxic. The toxicity is from the sulphur compounds, which are heat-stable.

My dog ate one macadamia nut. Are they going to die?

Almost certainly not from one nut. Macadamia toxicity onset is at ~2 g/kg body weight — a 20 kg dog needs ~40 g (about 16 nuts) to reach mild symptoms. One nut is well below threshold. But symptoms can develop at lower doses if the nut was in a chocolate-coated dessert (combined macadamia + chocolate stresses the cardiovascular system) — call your vet for that combination.

Is ibuprofen really that bad? It's OTC for humans.

It's catastrophic for dogs. Dogs metabolise NSAIDs (ibuprofen, naproxen, aspirin) much more slowly than humans, and the toxic dose is shockingly low: 50 mg/kg causes GI ulceration, 100 mg/kg causes kidney failure, 250 mg/kg causes seizures. A single 200mg Advil tablet is dangerous for a 5 kg dog. Never give human pain meds to a dog without explicit vet guidance.

What about peanut butter — I heard it can have xylitol?

Yes. Some brands of "no sugar added" or "all natural" peanut butter (notably Go Nuts Co., Krush Nutrition, Nuts 'N More, P28) contain xylitol as a sweetener. Xylitol is the most dangerous common-household toxin for dogs — 100 mg/kg causes hypoglycaemic shock within 30 minutes. Read the label of any peanut butter before sharing with a dog.