Venoms, poisons, infections & allergies

‘Arty’. To me the word's got as much venom associated with it as 'wacky'. Alex Kapranos

Venoms, poisons, infections and allergies all have unique meanings, but are often confused in everyday language. Let’s break them down to understand what they actually mean.


According to the Oxford English dictionary:

A venom is a poisonous substance secreted by animals such as snakes, spiders, and scorpions and typically injected into prey or aggressors by biting or stinging.

A poison is a substance that is capable of causing the illness or death of a living organism when introduced or absorbed.

So basically, if you bite it and die, it is poisonous; if it bites you and you die, it is venomous. Venomous creatures actively inject chemical toxins via fangs, spines, stingers, or similar, into their victim. Venom is used by animals either as a defence mechanism, to counter an attack by an often larger animal, or as a way of catching prey. In some cases, the lethality of the venom is absurd: for instance, just a single drop of the inland taipan’s venom can kill about 100 adult humans. Venom is typically stored in specialised glands inside the venomous animal’s body, and in some cases is used to aid digestion of prey.

By comparison, poisonous animals secrete harmful chemicals, but are only transmitted to their victim if the victim eats or touches the poisonous plant or animal. Similar to venomous animals, even extremely small poisonous critters can have an enormous impact. For instance, the posion dart frog only measures 2 inches but has enough skin toxins to kill about 10 adult humans.

Poisonous substances and venom generally work by disrupting some kind of biological function of their prey or victim. Three of the most common types are neurotoxins, hemotoxins and cytotoxins.

  • Neurotoxins affect the nervous system with the main aim of killing by paralysing the heart and/or lungs. Signs and symptoms include suppressed heart function and breathing, as well as vomiting, paralysis, convulsions and muscle cramps. Critters that use neurotoxins include scorpions, paralysis ticks and cobra snakes.
  • Haemotoxin/hemotoxins affect the blood and tissues of the body and has the ability to break down blood cells and body tissues. Signs and symptoms include severe internal bleeding, major organ failure and the seeping of blood from body orifices such as the ears, nose and eyes. Critters that use hemotoxins include vipers and pit vipers.
  • Cytotoxins cause spontaneous death of the body cells and severe damage to body organs. Signs and symptoms include excruciating pain and major swelling of body tissues. Some jellyfish use cytotoxins.


Our skin is an extremely effective barrier to infectious agents such as bacteria. However, if the skin is pierced through an injury, scratch or bite, the wound is susceptible to infection. Ordinarily, germs like bacteria and viruses live on our skin without causing trouble but if the skin becomes broken, these germs move into the more sensitive tissues underneath and can start to multiply and spread, leading to an infection. Infected wounds left untreated can spread and quickly become a serious medical condition.

Any animal attack like a bite or a sting where the skin has been broken has the potential to become infected, and must be treated with this in mind. Having said that, if there is any risk at all that the bite is venomous (e.g. an unidentified snake or spider), then treating the patient for venom is the priority, and any infection risks are considered secondary.

Bites from some mammalian species carry the risk of transfer of infectious diseases like tetanus, Hep B from human bites and Australian bat lyssavirus (ABLV) from bats, and appropriate medical follow up must be taken.


With any type of bite or sting there is the potential for an allergic reaction. An allergic reaction is the body’s response to an invading substance. Our immune system gets activated when it detects foreign objects, and mobilises resources (including white blood cells) to the area to cope. In some cases, our bodies get this wrong, and overreacts. It can be from something that does not normally upset other people, but often people with allergic reactions don’t know they are allergic until they are affected.

There are two stages to developing an allergy. The first stage is sensitisation, where the allergen is recognised by the immune system and antibodies are made to fight it (even though the allergen is harmless).

The second stage is when the allergic reaction kicks in. Since the immune system retains the memory of the allergen, whenever it has contact with that allergen again even in the tiniest quantity, the body responds. That’s why people with hay fever have coughs, runny nose and flu-like symptoms at pollen season, or the tiniest amount of peanuts in food can affect someone with a peanut allergy.

Allergic reactions can occur after a bite or sting, where the body overreacts to any new substances that have been detected, be that a poisonous substance from a venomous creature or an infectious germ after the skin has been broken.

The main difference between an irritation like small swelling from a mosquito bite and an allergic reaction like hayfever is that an irritation is localised to the affected area. By comparison, an allergic reaction spreads to other parts of the body.

Anaphylaxis is a severe allergic reaction where the patient experiences extreme allergic responses including itching, swelling and shortness of breath. Anaphylaxis must be treated immediately, as it can cause death if untreated.

FUN FACT: Did you know that our cute and cuddly Platypus (Ornithorhynchus anatinus) is armed with venomous spurs?
Male platypus have a sharp barb located above its rear webbed feet. Used mainly during the mating season, males inject painful venom into their rivals during a fight.

Reports of humans being stung by platypus are rare, but do exist. While not fatal, stings are reported to be extremely painful with the potential to cause permanent disability around the affected area. Interestingly, individuals held in captivity do not produce venom, making it challenging for scientists to collect and reliably test the properties of platypus venom reliability.

So don’t be fooled by it’s cute and cuddly appearance, male platypus are venomous! As with all animals you see on a bushwalk, respect them from a distance and leave no trace.