Why Do We Itch?
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By Samantha H.

Did you know that scientists did not really know what causes itching until about a decade ago? Scientists’ first attempts to find a good conclusion about itching came about in the 1970s and 1980s. When they studied the relationship between plants, such as poison ivy, and itching, they concluded that if one’s skin comes in contact with the plant’s toxins, the skin releases a protein called histamine from cells that cause swelling, reddening, and itching. Histamine tells our itch nerves to send information to the spinal cord which processes the information and then sends it to the brain. The brain’s activated sites when we itch are similar to the ones activated when we are in pain.
Itch-sensitive fibers were first discovered in 1997 by Martin Schmelz. He has now found new fibers that arouse itchy feelings differently than histamine-sensitive nerves that he discovered before. "It is evident that there is more than just one type of nerve fiber involved in the itch sensation," Schmelz said. "A lot of information has been generated related to histamine-sensitive itch fibers and currently new types of itch fibers are being investigated, which might help to explain the chronic itch condition more completely."
Now, are you wondering why we scratch ourselves when we itch? Neuroscientist Earl Carstens says that we may scratch because it might turn on nerves that stimulate pleasure systems in the brain. Even though some people think scratching feels good and is a huge relief, it can actually really hurt someone suffering from atopic eczema or dermatitis which is a skin condition caused by anything that can irritate one’s skin. If someone scratches too much or too hard, it can cause bleeding and infection.
Now that you have read my post, take my poll. Here are some other questions: Can you find any other explanations of why we itch? What other diseases cause people to hurt themselves when they scratch?

Student Expectations
How Will I Meet This Expectation?
How Did I Meet This Expectation?
Demonstrate ability to
evaluate sources of
biology information on
the internet

- I will use and contribute to the credible
sources sources section on the wiki page
- I will use websites that are depenable
such as .edu and not websites that are
bias, such as .gov
- I contributed to the credible sources section
by verifying Erik's sources.
- I checked Ryan D.'s source and Will B.'s
- I contributed to the credible sources section
by verifying Jennifer's sources.
- I put my two sources on the credible sources page and
they were verified by many different people.
Demonstrate an ability
to read and understand
current biology news
- I will research intently and find things about
every part of all the articles I am researching
and make sure everything is current
- I researched intently for every part of my post.
- My news was current. (November 2008)
- I read the articles, understood the information, and
then wrote my own post in my own words.
- I used more than one website to make my post more
Demonstrate proper
use of online resources

- I will use a creative commons photo
- I will hyperlink correctly
- I hyperlinked in my post.
- I used these two websites: &
- I hyperlinked a creative commons photo in
my post.
Publish work that is
available for peer-review
- I will submit my posts on my blog page so
other students can read and review them
- I will publish my work on the class blog
- I published my post 'Why do we itch' as
a discussion and Caitlin, Rachael and Skye
have peer reviewed.
Discuss published work
with a practicing biologist
in that particular field

- I will e-mail a biologist in the field and ask
them to review my post
- I e-mailed Laura Sanders because she wrote the
post that I researched and linked to in my post.
Provide constructive
peer-review to
- I will write comments to their blog posts
- I will try to edit someone's post on their
wiki page
- I gave constructive criticism to Rachael's post, Ryan
D.'s post, Will B's post, and Urmi's post.
Discuss in-class

- I will make a post relevant to something we
discussed in class
- I commented on Caitlin's post about low vitamin D levels
in Arab-Americans on the class blog.
Apply creativity
to work
- I will make a bitstrip or create a poll
- I made a poll for my blog post.
- I made a video for my blog post.

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My favorite thing we studied this year was animal behavior (innate, learned, imprinting, etc.) because we got to experiment with the cockroaches and watch cool videoson the animal's behavior to each other. It also helped us with the scientific experiment terms such as dependent variable, independent variable, control, etc.

Hey; I'm Sammy. My life is pretty much my friends and dance. I love sleepovers with my best friends, watching ballets, Christmas, snow, food, sleep, and pink. (: