Benign most of the time, these bites cause more serious symptoms in the event of an allergy or if the insect is a carrier of diseases.
Calvary of summer evenings, mosquitoes are probably the insects that “ sting » most frequently. However, we tend to forget that stings, or bites, can be caused by several thousand species and that some also occur in winter. When should you be worried about a bite? Can we learn to recognize it? How to deal with them and prevent them? Explanations and advice with Pr Olivier Gaide, head of the onco-dermatology unit of the dermatology and venereology department of the Vaud University Hospital Center at the University of Lausanne.
Insect bites: what are the symptoms?
“ Often inseparable from each other, insect bites are characterized by the appearance of small pink or red pimples (papules) on the skin with a diameter not exceeding 2 cm in the absence of an allergic reaction “, explains Professor Olivier Gaide. The symptoms are also variable depending on the type of insect. Redness, swelling, warmth, pain and itching are the most common reactions and are usually symptoms of inflammation caused by the sting or bite.
How do I know which insect bit me?
“ Very often, the visual aspect of an insect bite does not make it possible to identify the species that caused it, even for practitioners and specialists in entomology. “Admits Professor Gaide. On the other hand, depending on the mode of action of the insect, the symptoms experienced by the patient will be different.
In the family of Hymenopterathem beesthem wasps and hornets, which sting to defend themselves, inject their venom by sticking their stinger into the skin. This causes blistering or redness as well as severe pain.
The mosquitoesthem Bedbugs and the fleas bite for the purpose of feeding and, unlike wasps, their stings are painless. Because they do not want to be disturbed in the middle of a meal, these species will therefore be rather discreet. “ It is the females who are usually in search of blood, because they need to reproduce, where the males are harmless and feed only on water and nectar “says the doctor. During a blood meal, the insect injects small amounts of saliva which have an anesthetic effect. Consequences ? “ Our immune cells recognize mosquito saliva proteins as a foreign agent and will defend themselves by secreting histamines, an inflammatory mediator that increases the diameter and permeability of blood vessels “, explains Professor Gaide. The resulting edema appears on the skin in the form of a papule: it is the strongly itchy mosquito pimple.
One can usually differentiate the bedbug bites and mosquito to their number: Bedbugs will often be said to take a starter, a main course and a dessert because during a blood meal, which usually occurs at night, they will tend to bite three times in a localized way, which produces an alignment of three pimples on the skin says the dermatologist.
About the ticks, they feed by pushing their head into the epidermis. It is therefore possible to recognize a bite by the presence of a small black dot at the level of the bite corresponding to the head which has detached from the rest of the body.
More rare, bitesspiders have different appearances depending on the species and the toxicity of the venom. Often, they result in swelling of the skin, redness and itching, even “plates» small red dots very close together.
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What insects bite in winter?
In general mosquitoes do not survive the winter or at least the number of individuals is considerably reduced due to temperatures not favorable to their reproduction. Some females are able to make fat reserves, find shelter (subways for example) and enter a slowed down stage of life (diapause) in order to prepare for sunny days. “ The bites in winter are rather the fact of insects that live indoors such as bed bugs and fleas “says Professor Gaide.
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When should you worry about an insect bite?
In general, insect bites are mild and resolve naturally after a few days without leaving a trace. On the other hand, an injection proves to be more dangerous in the event of allergic reaction. “ People allergic to the venom of wasps or bees or to other insects have a higher risk of having anaphylactic shock or angioedema which corresponds to a swelling of the throat », Warns the dermatologist. Such reactions can cause breathing difficulties, malaise, sweating, drop in blood pressure, vomiting and even life-threatening. In this case, call the emergency services immediately.
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On a completely different scale, particularly in mosquitoes, there is a risk of transmission of viral diseases (chikungunya, dengue fever, Zika, Japanese encephalitis, West Nile fever), bacterial (borreliosis, rickettsiosis) or parasitic (malaria, lymphatic filariasis). This can lead to serious complications such as high fevers, vomiting and diarrhea in the case of malaria.
Some ticks are also vectors of a infectious diseasethe Lyme borreliosis, also called Lyme disease, which can have long-term neurological consequences. “ In case of secondary appearance of redness extending gradually over several centimeters (or any abnormal behavior of the area), it is advisable to consult thinking of this disease », warns the doctor.
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Why shouldn’t you scratch?
“ This is likely to cause lesions and increase the risk of superinfection and abscess formation. This is the main reason why it is recommended to avoid touching a bug pimple “recalls the doctor. But then how to explain the relief caused when we scratch a bite? In an article published by the journal Journal of Investigative Dermatology in 2015, American researchers showed that the reward and satisfaction system is activated in the brain of patients with chronic itching. Despite this false good impression, we can thus quickly become addicted because the brain interprets the gesture of scratching as a pleasure. However, repeated scratching also risks intensifying the itching and damaging the skin by preventing it from healing properly, and even increasing the pain felt.
What to do in case of a bite and how to avoid them?
“ For any sting, it is advisable to disinfect the inflamed area well. As for the relief of stinging symptoms or pain, we will favor anti-inflammatory ointments advises Olivier Gaide. Beware, however: anything anti-venom pumps are discouraged, as these devices are misused and do not remedy the problem. »
To protect against bites, wearing long, loose clothing is still one of the best solutions because they prevent access to the skin, especially in the case of mosquitoes. It is also possible to use repellent products available in pharmacies.
In the case of ticks, which live more in the countryside or in the forest, it is strongly recommended to inspect your body after a walk and carefully remove the animal if it is still present on the epidermis, being careful to remove the head well. A pharmacist or other healthcare professional can help you if you are unable to remove the residue, and inform you about vaccination against tick-borne encephalitis if you live in an area where this virus is endemic.