|MadSci Network: General Biology|
Well, you almost guessed right. It is our skin's sensory function, that is responsible. Now, one of the major functions of the skin is to protect the body from anything outside that might harm it. So, the skin senses the grass as something which might cause it harm. There are small receptors on the skin which pick up these sensations and accordingly try to get away from the harming thing. So, it makes you itch, which persuades you to get up and thus, unconsciously, you comply to the body's senses by getting away from the grass. But, the thing is, this response is highly variable in people. Some people might not feel the itch at all. This is all an individualistic response of the body. Something like you get more sick than others for a particular disease, or you have to take medicine for a longer time to cure yourself than someone else, who might get cured just as easily.
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