MadSci Network: Medicine

Re: What happens when we scratch our mosquito bites?

Date: Mon Jun 21 07:49:40 2004
Posted By: June M. Wingert , RM (NRM), Associate Scientist
Area of science: Medicine
ID: 1085479779.Me

That was a good question and one that is of great concern right now due to 
the increase in West Nile Virus.
Bites may become infected from excessive scratching allowing bacteria to 
enter the bite and cause the infection.
Other concerns of the mosquito bite are allergic reactions from mild 
itching and swelling to the more severe swelling and difficult breathing.
Continual scratching may also prolong the symptoms.
Why does this happen? Your body contains special cells called mast cells. 
When they are irritated, such as being scratched, they release all sorts 
of chemicals. One of these is called histamine. Histamine causes tiny 
blood vessels to release blood into surrounding tissues. This causes the 
area to look red, feel hot and become swollen. The blood cells can help 
fight infection in the tissue, but the swelling can put pressure on 
nerves, causing more itching or pain. Scratching a mosquito bite releases 
histamine. Besides causing swelling, histamines sensitize nerves, making 
sensations such as pain or itching more intense. Scratching actually makes 
the itching worse. The more you scratch it, the more histamine you release 
and the more it itches. A trick that I learned is to use your fingernail 
to press into the center of the bite several times, making a star shaped 
pattern. This helps disperse the mosquito spit (Yes, the initial itch is 
caused by mosquito spit.) without releasing too much histamine. 

The histamine reaction can also be triggered by things you are allergic 
to. It may just be a yummy strawberry or peanut butter, but if you are 
allergic, your body mistakenly identifies it as something dangerous. This 
triggers the histamines, and you get a rash or worse. A histamine reaction 
in the airway can cause the tissue in your nose, throat and lungs to 
swell. That makes it difficult to breathe. When that happens, we take 
something to stop the histamines, an antihistamine. Many medicines for 
colds and flus contain antihistamines. Some people are so allergic that 
they have to go to the hospital to control the reaction.

Check out the following sites for more information on what happens when we 
scratch our mosquito bites. 

There is a wealth of information contained in the following links. - 28k jsp?type=6&startQid=3565&endQid=3664 - 
51k - Jun 19, 2004

Thanks for taking the time to send in a question to the Madsci org.

June Wingert

Associate Scientist
Lexicon Genetics
The Woodlands Texas

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