Spider Bite

, ie an "irritation with redness and swelling. Less often, severe local pain, systemic toxicity or allergic reactions may occur. Rarely, the skin wound may become necrotic.

The spider bite regresses without special treatments, in a relatively short time, except in cases where complications of medical importance are required.

If the injury does not cause too intense symptoms, simple first aid maneuvers can be implemented to limit the discomfort (eg application of ice, rest and lifting of the limb). In the event that a more severe reaction develops (allergy or systemic toxicity) after the spider bite, it is advisable to seek immediate medical attention.

of the victim.

Man is not among the potential prey of these animals, which tend to hide in their shelters or flee when disturbed. Almost all bites inflicted on humans occur when the spider is inadvertently trampled on bare feet or introduces a hand into a piece of clothing or between the sheets, where the animal is hidden.

Although 98-99% of spider bites are harmless, it should be noted that, in the remaining cases, this event involves necrotic wounds, systemic toxicity and, more rarely, death.

, but have two chelicerae, formed by two segments each:

Fang (or spike): it is sharp and sharp, to penetrate deep into the skin, fur or exoskeleton of the prey.
Basal portion: includes poison glands and the constricting muscles that surround them; the latter are voluntarily contracted by the spider to cause the release of the venom, which through the fangs will be injected into the wound caused by the bite.

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During the bite, the spider knows how to control the amount of venom inoculated into the victim and can adjust the dose according to the circumstances. For the arachnid, in fact, producing poison has a significant cost in terms of energy. Also for this reason, spider bites to humans are often free of poison ("dry bite"): the arachnid attacks only as a last resort, if he has no other choice.

The venom inoculated by spiders can be neurotoxic (attacks the nervous system, inducing paralysis of the prey) or necrotoxic (affects internal organs and tissues around the wound, triggering a partial digestion of the part involved).

Spider bite towards OTHER ANIMALS. In nature, the spider is a predator that feeds mainly on other arthropods (insects, other spiders, myriapods, mites, etc.). The bite is, therefore, a means of overwhelming its prey: the arachnid inoculates a poison with which it immobilizes or kills the victim, before feeding on it. Although the bite and the possible injection of venom are also used for defense, therefore , these means represent the main way in which the spider obtains food.

Spider bite to MAN. As far as humans are concerned, the effects of the venom inoculated into the wound during the bite is the most significant element in the medical field. Some spiders are considered very dangerous precisely due to the fact that they possess particularly harmful poisons for man, already in the small amount that can be injected with a single bite. Fortunately, not all spider bites involve the inoculation of venom.

Dangerous spiders in Italy

In the world, the species of spider considered dangerous for man are about 200 (out of over 42,000 of those existing), among these, there are potentially lethal arachnids, such as the banana spider or the black widow.

In Italy, the species whose bite is of medical importance for humans are mainly three:

Malmignatta (Latrodectus tredecimguttatus): also known as the Falangio di Volterra, it is recognizable by its rounded body and the presence of the characteristic red dots on the black back. In our country, the L. tredecimguttatus it is present in the Mediterranean regions, between the low vegetation of the woods and the scarcely frequented ruderal areas. This arachnid produces very resistant webs of irregular shape and, usually, does not nest inside the houses.
Violin spider (Loxosceles rufescens): also called hermit spider, has a 7-9 mm body, yellowish-brown in color, with long legs. This species is widespread all over the world; in Italy, it is mainly present in the Mediterranean area. The violin spider is a nocturnal animal; during the day, it remains holed up in crevices and crevices. In homes, this arachnid prefers dark and sheltered environments (behind furniture, baseboards, under boxes of cardboard or even inside gloves, shoes, attics and basements etc.).
Tarantula (Lycosa tarentula): it is found mainly in the central and southern areas of Italy; it causes a very evident, swollen and bluish sting. However, the bite of this spider is less dangerous than that of the violin spider and does not cause fatal reactions. Most tarantulas are covered in black and brown hair, but some species display more vibrant colors.These spiders prefer to live in dry soils in which they burrow which they then carpet with their web.

, fever, headache-and-dizziness, fever, sweating and widespread, itchy skin rash.

Systemic symptoms generally subside within 24-48 hours, while local symptoms subside within a few days.

Bite of the violin spider

The bite of the violin spider is initially painless and there are no evident alterations in the affected area. In the following hours, a red lesion begins to appear with itching, burning and tingling; in the following 48-72 hours, the wound can ulcerate, giving rise to necrosis and eschar of the tissues located near the bite (cutaneous loxoscelism).

Toxic reaction to the bite

Spider bite with necrotoxic venom inoculation can induce a systemic reaction, which manifests itself with:

Nausea, vomiting and abdominal pain;
Joint and muscle pain
High fever
Hemolysis (breakdown of red blood cells);
Reduction of platelets.

This type of poison is possessed by the violin spider and the malmignatta.

The inoculation of the neutotoxic venom with the spider bite can induce:

Restlessness;
Insomnia;
Muscle spasms and cramps;
Respiratory difficulties.

In severe cases, the toxic reaction to the spider bite can induce:

Weakness;
Cardiac arrhythmias;
Hypertensive crisis;
Pain in the lymph nodes;
Pharyngitis;
Abundant salivation (drooling);
Disorientation, confusion and loss of consciousness.

Spider bite allergy

In previously sensitized people, spider bite can induce a local allergic reaction, characterized by erythema, extensive edema, and pain.

Other times, the allergic reaction to the spider bite can involve different systems of the organism and induce systemic manifestations, including: generalized urticaria, angioedema, breathing difficulties, palpitations, nausea and abdominal cramps.

In severe cases, anaphylactic shock can develop after a spider bite. This is characterized by a marked and persistent reduction in blood pressure, which can lead to numbness or loss of consciousness, dizziness and cardiac arrest.

Possible complications

In addition to the inoculation of the venom, the spider bite can carry anaerobic bacteria in the tissues which, as they develop, complicate the course of the lesion with possible progressive necrotizing fasciitis.
In severe cases, the general reaction to the spider bite can be complicated with difficulty in breathing, bleeding, kidney failure and liver damage.

of allergic reaction, toxicity or necrosis.

Warning signs

Some symptoms associated with the spider bite should be interpreted as alarm bells. The sudden onset of these manifestations or their progressive worsening, should prompt you to consult your doctor within a short time:

The spider bite area is painful, red, hot, swollen and surrounded by a pale, bluish-red or purplish halo;
Itching, sensitivity changes and dark-colored crusts (eschar) appear at the site of the lesion and in the surrounding tissues;
After the spider bite, systemic symptoms begin, such as nausea, vomiting, muscle weakness or fever.

cold or by immersing the affected area in fresh water to relieve pain or discomfort associated with spider bite. The ideal would be to have a first aid kit available, equipped with ice that can be activated instantly (you can buy it in a pharmacy, a drugstore or a supermarket).

In general, then, it is useful:

Do not manipulate or incise the spider bite site;
Wash the wound thoroughly with soap and water;
Do not apply aggressive disinfectants;
Pay attention to the appearance of symptoms, even if the spider bite was not initially felt (possibly, document the lesion with a series of photographs, to monitor its evolution).

When the symptoms of spider bite tend to persist, however, it is always necessary to consult a doctor, who may indicate the use of analgesics (to reduce severe painful symptoms) or the application of cortisone-based creams (to reduce itching and inflammation). Depending on the case, it can also be useful for the use of antihistamine lotions, antibiotics, NSAIDs, patches with lidocaine or other topical anesthetics.

If the symptoms of the spider bite immediately appear serious, however, you should call 911 or contact a poison control center. Depending on the type of spider that caused the bite, in fact, it may be necessary to administer a specific antidote, capable of blocking the action of the toxin. For moderate to severe wounds, surgery may be necessary.

Attention! If possible, catch the spider and, keep it in a closed jar, take it to the ER for recognition. Even if crushed or stepped on, the arachnid can be identified.