Aloe vera is an indoor plant and is considered poisonous (especially its sap). Its active substances – some of which have a strong laxative effect – mainly attack the lining of the stomach, the kidneys and the uterus¹. Symptoms of poisoning can appear after eating large quantities of the plant.

Consequences: Vomiting, bloody diarrhoea, increased peeing, blood in the urine, lethargy, possible miscarriage.

The leaves, stem and especially the bulb of the “true amaryllis” – also called “belladonna lily” – are highly poisonous³. They contain alkaloids⁴ that cause symptoms of poisoning even when small amounts of the plant are eaten.

Consequences: Nausea, drooling, abdominal pain, vomiting, colic, diarrhoea, heart arrhythmia (slowed heartbeat), movement disorders, tremors, convulsions^5,6.

This plant contains toxic ingredients that include atropine, L-hyoscyamine and scopolamine. It is one of the most dangerous plants, and every part of it is poisonous⁷. Its active substances target the eyes, the central nervous system and heart, the glands, the smooth muscles of the gastrointestinal tract, the bile ducts and the ureters.

Consequences: Vomiting, movement disorders, drowsiness, difficulty swallowing, diarrhoea, tremors, cramps, visual disturbances, shortness of breath, heart arrhythmia, abdominal pain, intestinal problems, respiratory paralysis, bloating⁸.

This plant is also known as the “flamingo flower”. The leaves in particular are poisonous to dogs and cats. It contains calcium oxalate crystals and oxalic acid⁹. Its active substances attack the mucous membranes that line the gastrointestinal tract, as well as those of the mouth and throat, among other things¹⁰.

Consequences: Irritation of the mouth and digestive tract, bleeding in the gastrointestinal tract, swelling of the upper respiratory tract (rare), drooling, pain in the mouth, difficulty swallowing, diarrhoea and vomiting; in cases where higher doses have been consumed, convulsions, movement disorders and cardiac arrhythmia can sometimes occur, as well as liver and kidney damage¹¹.

Azaleas are a type of rhododendron. The small, deciduous species of the plant are called azaleas, and the large, woody shrubs are called rhododendrons¹². These plants contain substances called grayanotoxins¹³ that can lead to cardiovascular collapse. All parts of the plant are considered poisonous, and ingestion of as little as 0.2% of an animal’s body weight can cause poisoning. (See also “Rhododendron” below.)

Consequences: Drooling, vomiting, diarrhoea, abdominal pain, loss of appetite; disturbed heart rate, cardiac arrhythmia, low blood pressure (hypotension), tremors, temporary blindness, seizures, coma and, in the most extreme cases, death¹⁴.

Boxwood trees contain various alkaloids^15,16 and a butter-like oil¹⁷ that make this plant poisonous to animals. Boxwood is classified as highly toxic¹⁶ (especially to horses and farm animals); the lethal dose for a dog is 5 g per kilogram of body weight in the case of the leaves, or just 0.8 g per kilogram of body weight in the case of the main alkaloid found in the plant (buxin). At first the alkaloids have a stimulating effect, and then they cause paralysis and lower the blood pressure¹⁸.

Consequences: Severe gastroenteritis, diarrhoea, vomiting, abdominal pain, convulsions, movement disorders, collapse and, in extreme cases, death¹⁸.

The main active ingredient of clematis is protoanemonin, a plant toxin found in the buttercup family¹⁹.

Consequences: Vomiting, diarrhoea, drooling.

All parts of the daffodil are considered poisonous, but the most dangerous of all is the bulb. It contains poisonous alkaloids²⁰.

Consequences: Vomiting, diarrhoea, abdominal pain, arrhythmia, convulsions, severe drop in blood pressure.

This plant belongs to the so-called Aaron’s Rod family. It contains insoluble calcium oxalate crystals²¹ and oxalic acid²², as well as plant toxins from the glycoside group. All parts of the plant are extremely toxic to animals. The active substances affect the mucous membranes of the gastrointestinal tract, the heart, the central nervous system and the muscles²¹.

Consequences: Severe swelling of the mucous membranes, blisters, drooling (after biting into it), as well as (after swallowing) vomiting, abdominal pain, colic, diarrhoea, breathing difficulties, heart arrhythmia and other serious symptoms²³.

The genus Ficus includes numerous plant species that are considered to be slightly toxic. Their active substances target the central nervous system and skin, as well as the conjunctiva of the eyes and the mucous membrane of the gastrointestinal tract.

Consequences: Vomiting, diarrhoea and (at high doses) cramps and paralysis.

The red foxglove (Digitalis purpurea) is a highly poisonous plant^{7, 24, 25}. Ingesting even small amounts causes symptoms of poisoning, and the fatal amount for a dog is around 5 g of dry leaves²⁵. Foxglove contains naturally occurring toxins that affect the heart.

Consequences: Tremors, muscle cramps, breathing difficulties, nausea, vomiting, diarrhoea, drowsiness, staggering, slowed heartbeat, heart arrhythmia, cardiac arrest^{26, 27}.

This plant, which is also known as “devil’s ivy,” contains insoluble calcium oxalate crystals²⁸, like other plants of the Araceae family. Biting and chewing this plant releases these crystals.

Consequences: Salivation, diarrhoea, vomiting, bleeding in the body, difficulty breathing and/or swallowing; if consumed in large quantities, cramps, high blood pressure, liver and kidney damage, heart arrhythmia and movement disorders may occur²⁹.

Hyacinths are considered slightly poisonous to dogs and cats³⁰. The calcium oxalates³¹ and alkaloids¹³ contained in the plant cause symptoms of poisoning. The most toxic part is the bulb: severe poisoning symptoms can occur if it is eaten.

Consequences: Vomiting, drooling, diarrhoea, irritation of the mouth and oesophagus, increased heart rate, changes in breathing^{2, 31, 32}.

The poisonous parts of ivy are the stem, sap, leaves and especially the berries³³. Ivy’s active substances irritate the mucous membranes.

Consequences: Drooling, vomiting, diarrhoea, abdominal pain³⁴.

Kalanchoe belongs to a group of plants that contain cardiogenic glycosides^{35, 36}. However, dogs and cats that eat Kalanchoe usually get sick with gastrointestinal irritation or upset. If a large enough amount is eaten, there is a risk of more serious symptoms such as changes in heart rate and rhythm, weakness and collapse.

Consequences: Salivation, vomiting, diarrhoea, heart arrhythmia, weakness, collapse, cardiac arrest.

This plant becomes increasingly toxic as it matures: it is poisonous when young, but very poisonous when mature³⁷. All parts of the plant are dangerous – especially the seeds³⁸. The alkaloids found in this member of the buttercup family have a neuromuscular blocking effect³⁹, causing paralysis.

Consequences: Drooling, colic, constipation, vomiting, stiff gait, slowed heartbeat, abdominal pain, paralysis, convulsions, heart failure, respiratory paralysis and, in extreme cases, death^{37, 38}.

Lilies produces beautiful flowers. Unfortunately for our cat companions, ingesting their pollen, leaves or even a small quantity of the water inside their vase could cause severe to acute kidney failure, due to their high toxicity. Cat owners should simply avoid keeping lilies, indoor and in the garden (Daylily, Asiatic lily, Japanese show lily, Stargazer lily, tiger lily, Rubrum, Red lily, Western lily, Wood lily, Easter lily).

Consequences: vomiting, anorexia, kidney failure⁴⁰

The flowers and fruits of the lily of the valley are highly toxic to animals⁴¹ because they contain cardiac glycosides. These affect the heart (in a similar way to foxgloves) and circulation in animals^{42, 43}.

Consequences: Dizziness, drowsiness, shortness of breath, cramps, vomiting, diarrhoea, slowed heartbeat, heart arrhythmia, circulatory collapse, cardiac arrest^{13, 44, 45}.

Monstera belongs to the Aroids (Araceae) like e.g. dieffenbachia, philondendron, anthurium/flamingo flower. Plants from this species contain similar substances which can lead to poisonings. The plants contain oxalate crystals, enzymes that break down protein and oxalic acid⁴⁶.

Consequences: Salivation, diarrhoea, vomitus, cardiac arrhythmia, difficulties in swallowing, damages of liver and kidneys, ataxia, bleedings⁴⁷.

This plant’s cardiac glycosides are very toxic to animals. Oleander is considered extremely poisonous⁴⁸ – eating even a small amount can prove fatal.

Consequences: Drooling, vomiting, (possibly bloody) diarrhoea, rapid breathing, coordination disorders, trembling, convulsions⁴⁹, vomiting, life-threateningly high levels of potassium, heart arrhythmia, fatal heart abnormalities⁵⁰.

Peonies are slightly poisonous. Their active ingredients target the mucous membrane of the gastrointestinal tract⁵¹.

Consequences: Vomiting, diarrhoea.

This plant contains insoluble calcium oxalate crystals⁵², similar to other plants of the arum family. When bitten, some of the main active ingredients are released into the mouth and throat, causing irritation in the mucous membrane⁵³. Eating larger quantities of the plant causes discomfort in the gastrointestinal tract and attacks the heart.

Consequences: Drooling, burning in the mouth, difficulty swallowing, diarrhoea, vomiting, heart arrhythmia, kidney problems, muscle twitching, liver damage, cramps⁵⁴.

Poinsettias are popular Christmas plants, with their distinguished white or red large flowers. Although their toxicity is not life threatening, it is recommended to keep them out of  cats’ reach. The milky white sap found in poinsettias contains chemicals called diterpenoid euphorbol esters and saponin-like detergents.

Consequences: Drooling, licking lips, vomiting, diarrhoea, skin irritation (including redness, swelling, and itchiness), eye irritation⁵⁵.

The rhododendron is highly toxic. It contains plant toxins (grayanotoxins) that impair the normal function of the skeletal muscles, the heart muscle and the nerves. All parts of the plant are considered poisonous, and eating as little as 0.2% of an animal’s body weight can cause poisoning. (See also “Azaleas” above.)

Consequences: Drooling, vomiting, diarrhoea, abdominal pain, loss of appetite; disturbed heart rate, cardiac arrhythmia, low blood pressure (hypotension), tremors, temporary blindness, loss of coordination, seizures and, in the worst cases, coma or death.

Spatiphyllum is another plant of the arum family (Araceae). Like the other plants of this family, it contains calcium oxalate crystals, as well as oxalic acid and its salts. The active ingredients have an irritating effect on the mucous membranes of the gastrointestinal tract, as well as on the heart, kidneys and central nervous system⁵⁵.

Consequences: Drooling, vomiting, diarrhoea, bleeding in the body, breathing and swallowing difficulties and – if a large amount is eaten – cramps, heart arrhythmia, damage to the kidneys and liver, low blood pressure, movement disorders⁵⁶.

This plant contains naturally occurring poisons that affect the heart (see also “Foxglove,” “Kalanchoe” and “Oleander”). These active substances (which resemble digitalis or digoxin) interfere with the electrolyte balance of the heart muscle⁵⁷. The severity of the poisoning will depend on the particular plant, the part of the plant that is eaten and how much is ingested.

Consequences: Nausea, vomiting, drooling, dilated pupils, trembling, seizures, abnormal heart rhythm and heart rate and dangerously high potassium levels⁵⁷.

All parts of the tulip are toxic to animals, but the highest concentration of toxin is in the bulb. If parts of the plant or bulb are chewed or swallowed, irritation of the mouth and oesophagus may occur, as well as irritation of the mucous membrane of the gastrointestinal tract, resulting in impaired digestion of nutrients⁵⁸.

Consequences: Vomiting, drooling, diarrhoea, irritation of the mouth and oesophagus, increased heart rate, changes in breathing^{2, 13}.