Gemma Gaitskell
Dr Gemma Gaitskell (BVetMed MSc MRCVS, Royal Veterinary College, London)
Foods that are toxic to dogs

Dogs are very good at finding things to eat which they shouldn’t or persuading us to give them a little taste of our food. Giving your dog a little treat is often difficult to resist but there are some foods which are bad for, or can even be toxic and poisonous to dogs so should be avoided. Despite this there are also many human foods which dogs can eat perfectly happily and safely.

It is important to remember that if your dog does get hold of one of these foods, particularly a large quantity, and you are aware of it then you should take it to your vet immediately. Many of the dangerous and toxic side effects can be greatly reduced if the right treatment is given in time.

Common Foods Which Are Bad For Dogs

Although this is not an exhaustive list some of the most common foods which dogs get hold of which are bad for them include:


Chocolate is a food which is bad for dogs which many dogs either get hold of or are fed by owners who are unaware that it is bad for their dog. It is found many different formats, and the cocoa content varies greatly. On the whole, the darker and more natural chocolate is a greater risk to dogs. The compound that it contains that is responsible for its nasty side effects is called theobromine, which is a type of methylxanthine. The darker the chocolate, the higher the concentration of this compound, which explains their higher toxicity and why even a small amount of dark chocolate can cause side effects.

The reality is that a very small amount of most chocolates is unlikely to cause side effects, but if a dog eats large amounts or a small amount of very dark chocolate some side effects it causes includes:

  • Restlessness and hyperactivity
  • Vomiting
  • A high blood pressure and heart rate
  • Trembling
  • An increase in body temperature
  • Even seizures, collapse and death in severe cases


Although caffeine probably brings coffee to mind, it is also found frequently in many foods, energy drinks, medicines and supplements. Caffeine is a type of methylxanthine, similar to theobromine, which is found in chocolate. Where tea and coffee are concerned, problems are most likely to be caused if a dog gets access to tea bags or ground coffee. Energy drinks and supplements contain caffeine in a very concentrated form so can cause even more severe effects.

Some of the common symptoms seen in a dog that has ingested coffee include:

  • Restlessness and hyperactivity
  • A high blood pressure and heart rate, as well as unusual heart rhythms
  • Vomiting
  • A high temperature
  • Trembling and seizures
  • Collapse and even death

Grapes, Raisins, Currants and Sultanas

Grapes and other dried forms of them are toxic to dogs. Grapes and their dried versions are also commonly found in less obvious forms, such as in puddings, bread, cakes, juice and sauces. Despite the fact that a dog may seem okay after eating grapes, raisins, currents or sultanas, it is important to take them straight to the vet to try and minimise side effects.

Only a small amount of this fruit needs to be ingested by a dog to cause severe signs of toxicity. This toxicity affects the kidneys and results in kidney failure. If no treatment is provided and kidney failure develops a few days after then the consequences can be more serious. The amount that can causes toxicity can vary significantly between different dogs. Some of the more outwardly obvious signs that a dog has eaten grapes, currents, raisins or sultanas include:

  • Gastrointestinal signs, such as vomiting and/or diarrhoea, as well as a loss of appetite
  • Abnormal water consumption and therefore urine production
  • Dehydration
  • Smelly breath (halitosis)

Onion, Garlic, Leeks and Chives

Onion, garlic, leeks and chives all belong to the same family; the Allium family. They are commonly found in both their raw and cooked forms in many different foods. As they are often used in foods as a base ingredient it is easy to forget about them. However many recipes for soups, stews, pies amongst others contain them in a more concealed form. Some breeds of dog, particularly some Japanese breeds, such as the Akita and Shiba Inu appear to have a higher sensitivity towards the effects of onion, garlic, leeks and chives.

Garlic is approximately five times stronger than onions and many of the toxic effects are related to damage caused to red blood cells. This damage results in anaemia, amongst other digestive tract signs. Common signs of onion, garlic, leek and chive toxicity include:

  • Gastrointestinal effects, such as irritation in the mouth, vomiting, diarrhoea, abdominal pain
  • Dribbling and nausea
  • Lethargy, weakness and less tolerance to exercise
  • A high heart and breathing rate
  • Pale gums – an indication of anaemia
  • Collapse

It is important to remember that powdered forms of these foods can also be dangerous, and are less obvious than the fresh or chopped forms in foods.

Foods Containing Xylitol

Xylitol is a type of naturally occurring alditol (sugar alcohol) which is used as a sweetener. It is found in numerous different types of food, including chewing gum, sweets, mints, sweet foods and sugar free drinks, toothpastes and other sugar free foods. Dogs only need to eat a tiny amount of xylitol for it to cause severe consequences. Signs in dogs which have eaten something containing xylitol include:

  • Tiredness and weakness
  • Vomiting, black, sticky stools and jaundice
  • Collapse, trembling, seizures
  • In severe cases, even coma and death

It only takes around 10-15 minutes for a small amount to cause a dangerous drop in blood sugar levels. Larger quantities cause liver necrosis and then liver failure. If treatment is going to have any chance of being successful it must be given as soon as possible and as intensively as possible so it is vital to take your dog straight to the vet if you think it has eaten anything containing xylitol.

It is important to take blood samples for analysis a few days after treatment to assess liver function and monitor if there is any permanent damage. Ultimately, this depends on the amount of xylitol the dog has eaten.


Although most of know that dogs should not be drinking alcohol it is also found concealed in other foods where it may be less obvious. These foods can include things, such as unbaked bread dough which ferments in the dogs stomach, thus producing alcohol, fruit salads, trifles, soaked fruits and other puddings, as well as sauces just to name a few.

It takes a smaller quantity of alcohol to produce side effects in the dog than in people as dogs have a higher sensitivity to it. Alcohol affects the dog by causing blood sugar levels to become dangerously low and also influences blood pressure and body temperature. Some of the obvious outwards signs it causes which can be seen are:

  • Dribbling, retching, vomiting, bloated stomach
  • High heart rate, low blood pressure
  • Weakness, eventually collapse
  • Low body temperature
  • In severe cases, seizures, coma, respiratory failure and death

Macadamia Nuts

Until relatively recently it wasn’t known that macadamia nuts were toxic to dogs. The precise reason for their toxicity in dogs is still unknown, but it is thought they have an effect on the nervous system – particularly the control of movement. This means that signs are often seen in a dogs back legs first. Macadamia nuts are probably not something dog owners would typically feed as a treat intentionally, however, it is important to be aware that they are present in a more disguised form in things, such as biscuits and cakes. As with most foods that are bad for dogs, the symptoms macadamia nuts cause dogs to suffer from depend on how much of this food the dog has eaten. Some of these symptoms include:

  • Vomiting
  • Severe tiredness
  • A high temperature
  • Trembling
  • Stiff joints and even a sudden inability to walk.


Only some types of mushrooms are poisonous for dogs, this is dependent on the chemicals which they contain. The consequences of mushroom toxicity can vary from mild to severe depending on the type of mushroom and the way it affects an individual dog. Clinical signs of mushroom poisoning include:

  • Vomiting, diarrhoea and tummy ache
  • Loss of coordination
  • Trembling
  • Seizures

Ultimately, the wrong type of mushroom can cause both liver and kidney damage so should be completely avoided in order to be on the safe side. As with foods that are bad for or toxic to dogs, it is important to seek immediate advice and treatment. Remember that mushrooms may potentially be found out and about on walks, as well as hidden in foods.

Corn on the Cob and Avocado Stones

The side effects of corn on the cob and avocado stones are both mechanical as if swallowed whole they can cause the intestine to become blocked, resulting in serious consequences. Dogs that suffer a blocked intestine usually require surgery to remove the blockage, otherwise it can be fatal. In addition, avocados contain a chemical called persin, which although not toxic to dogs, can cause mild digestive tract irritability.

Apple Seeds and Fruit Stones

Apple seeds and fruit stones contain a chemical called cyanide that is released when they are digested. Although a dog would have to eat a fairly large amount to suffer consequences owners should be aware that the chemical compound cyanide is toxic. With this in mind, it is best to remove any seeds or stones before feeding any fruit as treats or as part of a home cooked diet.

Black and Other Types of Pepper

All types of pepper contain compounds which are irritable to a dogs digestive system. It is therefore best to avoid them as they can cause stomach upsets, vomiting and diarrhoea.

Milk and Dairy Products

Dogs often enjoy milk and other dairy products and although they are not poisonous and small amounts are unlikely to do any harm, it is best to avoid feeding dogs large amounts of them, as they often cause stomach upsets, resulting in vomiting and diarrhoea.

Mouldy Foods

It may be tempting to give your dog some mouldy leftovers and feel like they are not going to waste, and most dogs love them, however, mouldy foods can contain mycotoxins, which are produced by fungi, so don’t take the risk. Mycotoxins can be found on all sorts of food which is going off and can cause some severe signs, such as:

  • Vomiting
  • Distress
  • Lack of coordination and trembling
  • Seizures
  • Severe fever

If you have a compost heap, you should ensure that your dog cannot get into it as this can be another source of mouldy food. The good news is that most dogs can recover well if given intensive supportive veterinary treatment.

Common Foods Which Are Safe For Dogs

Ultimately, dog food is produced from many foods which we as humans also eat. In addition to these by-products which are left overs and unwanted parts from human food production are used. This means that the majority of human foods are usually okay for dogs to eat.

It is important to use common sense and avoid anything in excess, as well as all of the foods mentioned in the section above which are bad or poisonous for dogs. If you are unsure whether something is safe it is best to give it a miss or at the very least check out whether it is harmful before feeding it to your beloved dog.

Some of the food groups which are safe for dogs include:

  • Leans Meats and Fish: Cooked lean meats and fish provide a good source of high quality protein for dogs.
  • Carbohydrate Sources: These include cooked normal and sweet potatoes, rice and other types of grain.
  • Fruits and Vegetables: There are many fruits and vegetables which are safe for dogs to eat, excluding any which are mentioned in the previous section. It is important to remove any seeds or pips or large stones, which can release toxic chemicals or cause blockages.

The Importance of Feeding Appropriate Human Foods to Dogs

Although it may seem like there are countless foods which are unsafe to feed your dog these are in fact relatively few when you stop to look at all types of food. There are many safe options that make good treats for dogs or can be used to form part of a specially formulated and balanced homemade diet.

Good nutrition and safe feeding is essential for a dog’s overall health and well being as some side effects of unsafe foods can be particularly nasty and difficult to treat. If a dog is fed, or manages to get hold of a food that is toxic or unsafe it is essential to seek veterinary advice and treatment as rapidly as possible.