Spider bite: first aid and when to see the doctor

A spider bite is something that can happen to us at any time, when cleaning the house or going out to the field. But is there danger? Keep reading and we will tell you.

Last update: January 13, 2022

Faced with an unforeseen attack and a spider bite we can react, first with amazement and pain. Later, we will ask ourselves if it is dangerous, if we should go to the doctor or what to do.

It is important to clarify that not all species of arachnids attack humans; some are even so small that they cannot penetrate the skin. However, others can attack and their bites can be dangerous.

In this article we will learn about which arachnids we should be concerned about, how to recognize them, what are the most common symptoms, and what to do in case of a spider bite.

Are spiders poisonous?

Most arachnids are rarely dangerous; they don’t even bite or assault. And many are small, so much so that their fangs would not have the strength to penetrate human skin.

But when this happens, usually only minor injuries occur. Of course, there are also quite a few cases of spider bites that can be serious. Everything will depend on the species.

Black widow (Latrodectus mactans)

The black widow lives in different parts of the world: North America, Europe, North Asia. It measures about 4 centimeters and can be easily identified by the red spot on your abdomen.

The incidence of black widow bite is 3-4 cases per 100,000 people. However, mortality is 1%, according to studies.

Brown recluse (Loxosceles reclusa)

It is known as brown spider by its color. It is distributed throughout almost the entire American continent; It is also identified by a lighter colored spot on the back. It measures about an inch and is one of the most dangerous.

Tarantulas (Theraphosidae)

Tarantulas are quite widespread throughout the world. They do not have a particular habitat, because can be found in jungle or desert areas. They usually hide in holes in the ground, in logs or under stones.

They are identified by their large dimensions (almost the size of a human hand), as well as their hairy texture and protruding fangs. Despite their intimidating appearance, they are not usually aggressive.

Similarly, venom from different tarantula species is not considered dangerous. However, the bite of this spider can be painful and cause allergic reactions in people sensitive to its toxin.

Brazilian wandering spider (Phoneutria)

Despite its name, it is not limited to a single country, but lives throughout Central and South America. It’s as big as a tarantula but much faster and more aggressive. It is considered among the most poisonous in the world.

Hobo spiderEratigena agrestis)

It is distributed throughout the northern hemisphere, although prefers slightly dry climates. It is considered a dangerous species, not only because the bite of this spider can produce serious reactions, but because it is found even in domestic environments: window holes, hidden in furniture and appliances in the garage, in closets.

Camel spider (Solifugae)

They are so called both for their sand color and for the fact that found in desert climates. Although they also tend to inhabit thickets and wooded areas of America, Asia and Africa.

They are characterized by having a clip on the head and by having a rather elongated body. They measure between 5 and 8 centimeters, although some can exceed 15. Although they are not poisonous, with the forceps it can cause serious injuries.

Wolf spider (Lycosidae)

This species lives practically all over the world. It is distinguished by its two large eyes in the middle of the face.

They are usually the size of tarantulas and similar in appearance. They can be found in domestic spaces: in the garden, in the grooves of door and window frames. Its venom is not dangerous for humans, although it does produce some allergic reactions.



Jumping or jumping spider (Salticidae)

This is one of the most common house spiders. It is small (less than 2 centimeters), but its body is robust.

It has light spots on top. It appears suddenly on indoor or garden plants. The jumping spider bite is not poisonous, although it does cause reactions if you are allergic.

Spiders found in domestic spaces tend to attack by accident, when they feel threatened by human presence.

Symptoms of spider bites

Sometimes the spider bite is not noticeable until a while later. However, when this happens and they manage to penetrate the skin and inoculate the toxin, it can generate various health complications.

Of course, such reactions vary according to the species of arachnid in question. Among the symptoms of spider bites, some common and some not so common are the following:

  • Redness of the skin with inflammation.
  • Itching or burning with a sensation of heat.
  • Hives
  • Visible wounds with skin tears.
  • Blister at the puncture site.
  • Headache.
  • Muscle cramps.
  • Fever with chills
  • Drooling (from the bite of the Brazilian wanderer.
  • Purple skin around the bite (brown recluse).
  • Wound suppuration (vagrant).
  • Abdominal stiffness, cramps, nausea and vomiting (black widow).
  • Acceleration of the heart rate (tarantula).
  • Swollen neck glands (wolf spider).


First aid in case of spider bite

When it is detected that it is one of the non-poisonous species, various measures can be applied after the spider bite. These include the following:

  • Clean and disinfect the area to prevent added bacterial infections.
  • Apply local ice, in and around the bite for a few minutes.
  • Keep the chopped limb elevated to reduce inflammation.
  • Taking an over-the-counter antihistamine, such as diphenhydramine.
The cold localized to the bite relieves the symptoms. You can use ice wrapped in a cloth or cloth.

All of this works best if applied within the first 24 hours after the spider bite.

Risks and complications of spider bite

Spider bite symptoms tend to subside over timeeven without treatment. At most, some stay for a few days or a week. But seek medical attention if the discomfort does not go away or becomes more severe.

Your doctor may prescribe some treatment with antibiotics, corticosteroids, or pain relievers for infection, muscle spasms, or to decrease pain. A booster injection is also recommended to prevent tetanus. This may be required in camel spider bites.

Eventually, surgery can sometimes be done to remove tissue. One of the possible complications of hobo spider bite is necrosis.

This also happens with the bite of the Loxosceles reclusa, which causes rapidly progressive necrotic lesions that even lead to amputation of the affected limb. They can also cause systemic manifestations, such as coagulopathies, intravascular hemolysis, and kidney failure.

The bites of some species can cause tissue damage, although very rarely. In addition, deaths are not frequent; however, cases of deaths attributed to the Brazilian wanderer have been reported.

When to go to emergency services?

Call or go to emergency services if the bite was from a suspected dangerous spider (such as black widow or brown recluse). In the same way, if the person shows any of the following signs:

  • Anaphylaxis or shock anaphylactic.
  • Trouble breathing.
  • Severe or sharp pain
  • Area of ​​inflammation that spreads with red lines.

When in doubt, it will always be better to have a professional evaluation. Physicians are trained to distinguish one bite from another and apply the appropriate therapeutic approach.

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