Phonetic pronunciation of 七彩豬毛釘: chut choi ju mo deng
My mother grew up in a working-class family in Hong Kong.  On one hand, my mother’s family was living in an industrialzing culture; on the other hand, her parents came from Southern Chinese villages.  So there’s a lot of beliefs and practices that they carried over from their village lives.

My mother learned a folk medicinal practice from her mother when she had a fever as a child.  Her mother used an old folk remedy, the 七彩豬毛釘, to cure my mother of her fever.

The 七彩豬毛釘 is made of rice flour, hot water, and an egg.  The preparation of the remedy is really simple – you heat some water and add the rice flour and egg to it.  There is no specified amount of each ingredient that you have to put into the remedy.  You just have to create the right consistency that lets you knead the mixture into a piece of dough.  While it is still hot, you roll the ball of dough along the back of the sick person.

The person who prepared the 七彩豬毛釘 then breaks open the ball.  If the treatment worked properly, there should be tiny hairs of all colors stuck in the dough (七彩 means “rainbow” in Chinese – the hairs are also described as looking like pig-hairs, 豬毛).  My mother attests that she saw her mother break the ball open and found rainbow-colored hairs inside.  After the treatment, her fever reduced.
My mother recreated the treatment for me (I was curious), but since I did not have a fever, she was unable to actually apply the remedy.

What I find very interesting is that the remedy has a visual confirmation associated with it.  The remedy’s power comes from contagious magic — the illness of the patient transfers into the piece of dough when it contacts the patient’s skin.  My mother didn’t particularly remember any explanation as to why the illness would turn into rainbow-colored hairs, she just knows that it reduced her fever.  Nobody is allowed to eat the dough after the treatment either, which would make sense since contagious magic has transferred what’s causing the illness into the dough.