估计生石膏退烧的主要有效成分就是镁

镁（硫酸镁）可以用以缓解产妇发热，以及一般的缓解发烧，退热。美国有报道。镁易溶于水，石膏煮过之后，镁含量就大大降低。这可以解释生石膏煮过之后再煮就无效。但对治疗感染大概没有多少关系。

参见：

Magnesium during labor may reduce risk of fever in mothers and complications in babies https://www.asahq.org/about-asa/newsroom/news-releases/2015/10/magnesium-in-labor-reduces-fever

Shivering Treatments for Targeted Temperature Management: A Review  https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5882245/