Man and warm blooded mammals attract female mosquitoes who need blood for their eggs to develop. Skin secretions act as location beacons which a mosquito can detect at long range, and it navigates by a complex olfactory system.

The aromatic ingredients found in blood and sweat, which we humans find unpleasant, are attractive for insects. As are foodstuffs and drinks, especially sweet soft drinks; strong smells; concentrations of amino-acids; ammonia; lactic acid; light, and bright colours.

Allergic reactions
In some tropical countries insects and spiders are responsible for the transmission of more than 100 diseases, including malaria and yellow fever. And in Spain, an estimated 800,000 Spaniards suffer allergic reactions from bee and wasp stings. In fact between 15 and 20 people die very year from this cause.

After suffering a sting a person may experience slight or serious allergic symptoms. Slight reactions include itching, a rash or a swelling. If the reaction is more serious, symptoms may include feeling faint or sick, dizziness, debilitation, high blood pressure, wheezing, vomiting, unconsciousness and even death. In either case an allergy specialist should be consulted.

Not everyone reacts in the same way to an insect sting. Precisely for this reason the only way to know whether a person is allergic to stings is by going to an allergy specialist, who can carry out a full etiological diagnosis, based on a questionnaire, to gauge the seriousness of the reaction suffered; plus skin tests and analyses.

Practical tips
� Avoid going near rubbish bins.
� If you do any gardening apply an insect repellent.
� Do not go barefoot.
� Avoid wearing voluminous or bright coloured clothes.
� Do not wear very strong perfumes.
� If you are having a picnic in the country and you have a baby, make sure you�re a long way from the nearest beehive.
� When you get in the car make sure you don�t let insects in, and drive with the windows up.
� Don�t flap about if an insect is near. Bees and wasps only sting when they feel threatened.
� If you are stung by a bee, remove the sting with a fingernail but without pressing the poison sac to avoid making things worse.
� If you are going to travel to hot and humid lands, or tropical, African or Asian countries, take precautions. Find out which jabs you should have and get yourself a good first aid kit.

Treatment
� For bee and wasp stings immunotherapy is the only treatment which will prevent an allergic reaction. The treatment consists of applying an anti-allergic vaccine which is effective in more than 98% of cases. This vaccine contains minute quantities of the poison from the insect which causes the allergy. In this way the patient gradually builds up an immunological tolerance. The treatment can last for between three and five years and injections are monthly.
� You could also try using repellents. The most effective against mosquitoes, horseflies, mites, spiders and ticks is diethyl-m-toluamide or DEET. It should be applied every six to eight hours, or more frequently in cases of excessive perspiration. It acts directly on the insects� sense of smell and forms a gaseous layer over the skin, which makes it unattractive to insects.
� Consult an allergy specialist about the possibility of taking oral antihistamines.