Its quite easy, it most often occurs to whom doesn't prepare there vocals.
People who sing in very high notes could damage your vocal cord because, It's almost like screaming.
When it comes to singing anything can happen.
If your singing at a very high note it can almost be like screaming, which can be painful.
You're basically overloading your vocal cords.
That is also why it's important to practice, and prepare your vocals before singing in a very high pitch, well before you sing even if it's not in a very high pitch.
