|Educational/Dermatology - Mosquito and tiger mosquito bites and remedies |
Mosquitoes belong to the kingdom Animalia, the phylum Arthropoda, the class Insecta, the order Diptera, and the family Culicidae; about 2,700 species are found throughout the world. They are two-winged insects (Dipterae) capable of flying up to three kilometres in one hour.
The females have to suck blood from animals or humans in order to obtain the proteins necessary for the maturation of the 40-400 eggs they lay on the surface of still water such as ponds, marshes, puddles or even the dish underneath a flowerpot. The eggs hatch after a week to become larvae living just below the surface of the water, then pupae and finally adult insects that live for two weeks or so.
Some species transmit diseases such as malaria, yellow fever, West Nile fever and others. Now that malaria has disappeared from Italy, mosquito bites are considered irritating rather than dangerous; however, the arrival of new species of mosquitoes such as the the Asian tiger mosquito means that things are no longer so certain.
tiger mosquito or Aedes albopictus, which originated in South-east
Asia, arrived in Europe in 2000 and subsequently rapidly spread to many Countries.
They can be recognised by the fact that they are smaller and darker than our
mosquitoes, and have characteristic white stripes on their legs and back.
Their habits are also different from those of our mosquitoes: they not only
bite at dusk and dawn, but also during the day when the sun is still out, and
they often do so in swarms of hundreds. The liquid they inject is
particularly toxic and gives rise to an extremely itchy or painful skin
Mosquitoes are small but highly evolved insects. They have sensors for heat and smells that enable them to detect their victims extremely precisely even in the dark. During their evolution, they have learned how to seek out humans on the basis of their natural odours, but also their perfumes, the smells of cooking, and artificial lighting.
Although very dangerous in other parts of the world because of the diseases they transmit, mosquitoes are mainly nothing more than annoying in Italy. Mosquito bites lead to pomphi: i.e. that itchy swelling that lasts for 20-30 minutes. However some people, especially children, develop abnormal reactions that take the form of an intense swelling that can last for a number of days and leaves an itchy red nodule that may remain for some weeks.
The other problems associated with mosquito bites are that scratching may give rise to skin infections (impetigo), and the itching also makes it difficult to sleep and leads to daytime tiredness. As the consequences may be serious for children, the elderly and the sick, it is necessary to try to prevent mosquito bites.
There are three types of prevention: the environmental prevention of mosquito reproduction, keeping mosquitos away from domestic environments, and preventing the insects from reaching the skin.
The environmental prevention of mosquito reproduction is divided into the responsibility of health authorities for public places and the responsibility of individual citizens for private premises.
should take care to avoid allowing the pooling of water in which mosquitoes
can lay their eggs. The most typical places for these are:
In addition to mosquito screens at the windows and mosquito nets around the bed, this can be done by means of fumigators or spirals that use derivates of pyrethrum, a substance that is capable of paralysing mosquitoes. However, they are only effective in closed environments and, although they are not very toxic for humans, it is good practice to air rooms after their use. Other products based on essential oils that claim to keep mosquitoes often actually attract them. There are also some devices that emit ultrasounds, and lamps that use light to attract mosquitoes before electrocuting them (known as zappers), but they are not very efficient.
are prevented from reaching the skin by means of so-called
"repellents", which are substances capable of interfering with the
ability of mosquitoes’ sensors to detect blood vessels.
DEET (N,N-Diethyl-meta-toluamide) is the most widely used chemical substance in insect repellents, and a concentration of 10-30% provides good protection for an evening in the open air. Higher concentrations should be used in areas at risk of diseases such as malaria.
The more recently introduced picaridin is as protective as DEET, and is present in Bayer’s Autan line under the codename KBR 3023.
(para-Menthane-3,8-diol) is the only plant derivate approved in the USA as an insect repellent, although its action is very weak.
Insect repellents, which are applied directly to the skin and are partially absorbed by the blood, should be used respecting the following rules:
The last problem is the swellimg and itching caused by mosquito bites. If your attempts at prevention fail and you are bitten, it is necessary to avoid doing any more harm. People often have recourse to do-it-yourself remedies such as applying ammoniac or rubbing the bite with a piece of lemon, but the first usually burns the skin and the second makes it photosensitive so that it gets burnt in the sunshine.
Drugs are not very useful either: creams containing cortisone only start working after 30 minutes, by which time the itching has stopped, and those containing antihistamines are also photosensitising.
The only remedy that can be recommended is to apply 5% aluminium chloride gel, a powerful astringent and antiseptic: as it reduces the itching, the infections caused by scratching are avoided.