Reduced pain threshold

All kinds of stimuli that can cause pain are not painful when the stimulus intensity is very weak; the pain is felt only when the stimulus reaches a certain intensity. The so-called "pain threshold" refers to the minimum amount of irritation that causes pain. For example, we poured water into a bottle that can hold 500ml of water. When 499ml of water was filled, the water still did not overflow. If we continued to add water, it would overflow. Under physiological conditions, a person's weak stimulus to the pain threshold does not cause pain, but when the stimulus is increased to a certain level, if the intensity is increased, it will cause pain, just like water overflowing from the bottle. Of course, the pain threshold problem is more complicated than bottled water.