Neurotoxin vs. Cytotoxin: The Difference between Spider Venoms


Are Spider Venoms Usually Very Dangerous?

The spider venom is a mix of a lot of chemicals. Usually, spider bites are not as deadly as people think.  The composition of their venom is often only enough to paralyze small animals.

So the short answer is no, besides some species that can be very dangerous or even deadly, in most cases, there is no reason to panic if bitten by a spider.

However, there are spider species like the black widow spider (Latrodectus) and the brown recluse spider (or brown fiddler) that causes more than just skin allergies. Their venom is composed of more fatal components. Those can lead to necrosis, severe skin infections, or worse. So let’s discuss what it comprises so we know how to deal with it.

black widow venomous spider
A black widow spider. Credit to Ken-ichi Ueda, via Wikipedia.

What Are the Components of a Spider Venom?

The venom is released through the spider’s fangs called “Chelicerae” as they bite. These are usually composed of the following substances.

  • Venomous Peptides: A variety of peptides (small-chain proteins) are the major components of the spider venom, some of these are venomous and in a dose high enough to harm humans, in some cases.  These peptidic toxins can serve many purposes. Among these, paralyzing small animals, or help the spider in the digestion process.
  • Enzymatic and Non-Enzymatic Proteins: These, on the other hand, have a high molecular weight that usually act as agents to help spread the venom throughout the body of the bitten creature.
  • Small Molecules: Different mixtures and concentrations of active small molecules can bee found in venom. The most notable ones act as neurotoxins or necrotic agents. Other active compounds like serotonin can also be found in spider venom.
  • Other Components: Spider venom has other more common substances like salts, biogenic amines, and carbohydrates.  All of these contribute to might contribute to producing pain, or have other functions.
Neurotoxin vs. Cytotoxin The Difference between Spider Venoms
Neurotoxin vs. Cytotoxin The Difference between Spider Venoms

Most people develop an allergic reaction to many of these chemicals because they are foreign agents. Plus, these can dissolve tissues and cause pain.  Depending on the components of the venom, it can either be categorized as a cytotoxin- or neurotoxin-based venom.  So what is the difference?

Spider Venom: Is it Cytotoxins or Neurotoxins?

Two types of spider venom are found as harmful and dangerous to people. This includes venom composed mainly of cytotoxins and venom that consists of neurotoxins. The difference between these two types is obviously the nature of the main chemical components found within them and the physical damage that they cause to humans.


Cytotoxins are substances that have a toxic effect on cells.

Cytotoxins have enzymes and linear peptides that damage the cells and tissues of the prey. Insects that are charged with this venom are liquefied for the easy ingestion of the spider. In the case of humans, cytotoxins create blisters, inflammation, or lesions on the skin surrounding the bite (necrotic bite). Loxoscelism is the condition where necrosis of the skin and the spread of red blood cells occur. Other symptoms of this condition include fever, headache, and vomiting. Some of the spiders that secrete cytotoxins dangerous to humans include the recluse spider and the South African sand spider.

brown fiddler spider
Brown recluse also known as ‘brown fiddler’ or ‘brown violinist’.


Neurotoxins have a toxic effect on cells, but only a specific type of cells: neurons. They are destructive to nerve tissue.

Neurotoxins present in spider venom usually are proteins, disulfide-containing peptides, or polyamines. These chemicals paralyze and then kill the prey. They attack and immobilize the nervous system. Animals can die because of neurotoxins but rarely does it happen to humans. Only in extreme situations neurotoxins from spider venom kill people.

The condition known as Latrodectism is caused by neurotoxic venom that can cause muscle cramps, pain in the abdomen or chest, vomiting, and sweating. Out of the two kinds of venom, this is the most dangerous of all. The black widow spider or red back spider, the Brazilian wandering spider, and the Australian funnel web spider all have neurotoxins that can potentially harm humans.

What to Do When Bitten by a Spider

Generally, spiders are harmless, but being bitten by a spider is a whole different story. The type of spider should be considered when treating a spider bite. And in extreme cases, the spider should be captured to identify the venom for the proper medical attention. This is many times not possible, so it always helps to have in mind the clearest description possible of how the spider looks like. As we said, almost always, spiders will only attack and bite when disturbed, so there should be not such thing as getting bitten while sleep without realizing.

The first aid treatment to a spider bite is to wash the affected area with soap and water. When the bite is painful and inflamed, a cold compress on the wound can be helpful. Antihistamines and analgesics can be used to reduce pain and swelling.

Immediate medical attention is needed as soon as symptoms are detected, especially if the bite of the spider has neurotoxins or necrotic substances. The bite of the Australian funnel web, the red back spider, and the Brazilian wandering spider can be fatal to humans.

In any case, what you should not do is panicking. In most cases you are going to be perfectly fine even without serious treatment. But better be safe than sorry and if you spot any serious symptom, go get it checked out.

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