Since they were venturing deep into the jungle, the people of the Ghost Race brought with them a lot of smudge fat. This smudge fat, a mixture of a unique smoky oil, is made by blending smoke dust and animal fat and then adding a few spices, primarily used to protect the skin from mosquito bites.
The effectiveness of this smudge fat is extremely good. Although it's somewhat uncomfortable when applied to the skin, once it's on, it essentially forms a complete barrier against mosquitoes.
Cheng Ziang had a profound impression of this, as before applying the smudge fat, he would always hear the annoying buzzing of mosquitoes and flies around his ears. No matter how hard he tried to swat them away, these pesky little insects were relentless. If he let his guard down for just a moment, the mosquitoes would crawl into his ear canal, an utterly hair-raising experience.