What causes itchiness of skin

This dog feels itchy! Itchiness is a common trait found among most animals and almost all of them react to the itch stimulus by scratching themselves. 

So, what causes itchiness (also known as pruritus)?

As we all know skin is the first line of defense for us and acts as a barrier preventing any pathogens from entering the body. Apart from acting as a physical barrier, skin also has the responsibility of notifying the brain of any potential threats because almost all threats first come in contact with skin. To aid this communication, skin is equipped with lots of neural receptors.

Now it is obvious that skin is the only organ (yes, it is classified as an organ)  in our body that constantly comes across different kinds of irritants like body hair, dust, mites etc. These things usually don't pose a threat to the body, but the skin decided that it is better to be safe than sorry and thus treats any kind of irritation as a threat and signals the brain. 

As soon as an irritant is detected on the skin, receptors under the skin send a signal to the spinal cord which is then transmitted to the brain. This immediately triggers an itching sensation and a scratch reflex which causes us to scratch the itching area with finger nails. This reflex helps us to subconsciously remove the irritant from the skin. Interesting though, is the fact that many times we don't actually remove the irritant but the pain caused by scratching over powers the 'itch signal' sent to the brain and thus the brain at least ignores the itch signal. Since these irritants are not really threatening most of the time, the brain ignoring the itch signal after a while is not a big deal (if it is really irritating, the scratch reflex gets triggered again).

So the next time you feel an itch, remember that it is a built-in defense mechanism of your body against the numerous irritants and potential threats it faces every day. 

Trivia: Some time ago there was some confusion among scientists if itch should be classified as a form of pain primarily because skin sends both itch and pain signals using the same fibers. However, this idea was later denounced by the scientific community based on the observation that itch and pain basically elicit different responses (the former causes the body to withdraw while the latter triggers a scratch reflex)

Did the simple science for kids in this post make you a little smarter?
If you have any ideas / questions you want to learn about, please leave a note in the comments section. 
Would be glad to know if there are any inaccuracies in the article.

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