So why do the little blighters tend to head for your feet and ankles?
Mosquitoes, midges and horseflies all love odour. Even if you can't smell yourself, the cocktail of bacteria that is naturally found on our bodies, particularly our feet, are sensed and smelt by pesky biters up to 100 feet away. Entomologist Daniel L. Kline experimented with using dirty socks as a mosquito lure, and found his 3-day-old socks were irresistible to them. Specifically, it's the bacteria that grow on human feet that seems to draw a crowd.
Mosquitos in particular are heat seeking missiles. Anything warm, including your feet, are seen as a ready meal. Feet and hands are useful in temperature control of the body. Think how you stick your feet out of the duvet to cool off at night, or how your hands and feet are the first to feel the cold when it's frosty outside.
Once they land on you the puncture wound of a bite is usually injected with saliva from the insect. This is a chemical cocktail of substances designed to make blood flow quickly and painlessly to the bug as it tries to get its fill and avoid being squished. This is why you don't usually feel anything until it is too late..
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The worst thing you can then do is SCRATCH! But we can't help it.... especially when you are in bed and the bite is throbbing. Just one little scratch won't harm, but the more you scratch the more you scratch the more you scratch. Agh!
Scratching causes release of histamine.
Histamine is a chemical that the immune system uses to help protect the body’s cells against infection. The immune system is the body’s natural defence against illness and infection.
If the immune system detects a harmful foreign object, such as bacteria or a virus, it will release histamine into nearby cells. The histamine causes small blood vessels to expand and the surrounding skin to swell. This is known as inflammation and it can lead to nearby tissue becoming red and swollen. It can also affect the nerves in the skin, making the skin feel itchy.
Most bites (be thankful we don't live in a country with nasty diseases) will settle on their own within a day or two, particularly if you don't scratch!!!
A cold compress can help and anti histamine cream will help reduce the swelling and some of the itchiness.
If things persist then taking an oral anti histamine tablet can be useful.
Occasionally people who have been bitten can have a nasty reaction called anaphylactic shock which causes the body to over react to a substance and can be fatal if untreated. If someone displays symptoms of urticaria (hives - lots of very small raised red bumps clustered together), nausea, vomiting, hypo-tension or respiratory problems soon after a bite, dial 999.
Other complications can include a secondary infection to the site. I often see patients that have scratched a bite area and have blisters, swelling and weeping sores. If the patient is compromised with other medical conditions this infection can lead to potentially dangerous cellulitis which can require hospitalization and anti biotic.
Be sensible. Most bites settle on their own with nothing more than an anti histamine cream or tablet. If things start to look worrying, change rapidly or get worse, then consult a medical professional just to be on the safe side.
References
J Appl Physiol. 1982 Nov;53(5):1228-33.
Restoration of thermoregulatory response to body cooling by cooling hands and feet.
10 Ways to Guarantee You'll Get Mosquito Bites
How to Lure Bloodthirsty Mosquitoes
By Debbie Hadley,
| CAMERON WEBB, THE UNIVERSITY OF SYDNEY |
| MONDAY, 30 APRIL 2012NHS choices website |
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