Most spiders only bite if provoked. Usually, their bites only cause a mild reaction, such as a small, minor swelling, inflammation, or itching. On the other hand, some American spiders like the Black Widow or the tarantula can be fatal to humans.

Spiders are not insects. They are arthropods that are part of the arachnid family, like scorpions. “They have four pairs of legs and a body made up of two parts: the thorax and abdomen. They feed on other insects and trap their prey in webs obtained from the silk they secrete, ”explains Dr Catherine Quéquet, allergist.

Although we are familiar with the term bites, spiders do not sting. They bite and thus inoculate their venom to their prey or their attackers. “Their saliva is composed of enzymes distilled through their chelicerae, that is to say their hooks.” When they bite a human, it is usually for self-defense.

“We must distinguish between the spiders which are found in our homes in France, which more readily give local and moderate reactions, and the spiders with severe envenomation which one finds in South America or in Australia”.

Among them :

• black widows
• brown recluse spiders
• tarantulas

“The spider bites that we find in France generally give local and moderate reactions, itchy and fleeting which require the application of an antiseptic to disinfect and the taking of an antihistamine to avoid itching”.

Poor disinfection can lead to lymphangitis, as with any bite of blood-sucking insects. “It takes the form of a red streak going from the bite towards, for example, an axillary hollow in the inguinal hollow with the appearance of lymph nodes and fever requiring antibiotic therapy and sometimes hospitalization”.

Typically, the spider bite results in two closely spaced red dots, usually circled with a white border. The spider can sting several times.

“Depending on the species of spider (especially those from South America), we can also see contact urticaria with stinging hairs.”

Acute generalized exanthemous pustulosis (AGEP) is a rare condition characterized by an acute febrile rash, usually drug-induced. “Its occurrence during a spider bite has been exceptionally reported in the literature in the case of a spider bite of the genus Loxosceles, a family in which we also find the recluse spider (“ Loxosceles reclusa ”) or the violinist spider (“Loxosceles rufescens”) “.

“Strictly speaking, there is no real allergic reaction to spider bites but rather non-specific inflammatory reactions in our hexagonal latitudes”.

However, there may be an allergic reaction to spider venom such as angioedema (main symptoms: swelling of the lips, tongue, around the eyes, hands and feet, often associated with breathing difficulties).

The black widow, recognizable by the red dots on her abdomen, is extremely dangerous. “It secretes a toxin causing intense muscle or abdominal pain with increased sweating. Skin lesions are rather inconspicuous, but always precede neurological disorders ”.

Segestria florentina (Florentine Segestria) is a large black spider that lives in crevices in walls. It is recognizable by the green reflections of its chelicerae. It is mostly found in Mediterranean regions. “His bite is painful and leaves not only local inflammation but also the mark of the hooks.”

Other species of spiders can be dangerous such as cheiracanthes, lycosis of Taranto or tarantula or the violin spider.

“These poisonous spiders cause an immediate reaction, swelling of the stung area. It is then necessary to inject an anti-venom whose effectiveness is not optimal depending on the spider in question ”.

A doctor should be consulted in all these cases which go beyond the small local reaction: headache, nausea, fever, muscle numbness, stiffness in the joints, dizziness … “The doctor will first look for a trace of a sting on the body then perform a blood test to identify the injected venom ”. Whenever possible, try to catch it and identify it.

The treatment for spider bites depends on the type of spider. In the case of mild bites, it is usually sufficient to disinfect the bite. Pain relievers, antibiotics, and antihistamines can be given to help with allergic reactions. If it is a dangerous spider, an antivenom should be administered.