The proteomics results confirmed, among other things, the presence of many popular ingredients used in the recipes, such as beech, watercress, and rosemary traces found next to hair loss remedies—commonly attributed to an “overheated brain—along with cabbage and radish oil, chicory, lizards, and, um, human feces. (Just how badly do you want to grow back that thinning hair?) The manuscripts also include recipes for blonde hair dyes. The analysis revealed traces of plants with particularly striking yellow flowers on those pages. “That is a common theme in cosmetic and medical discourse at the time,” said Hanss. “The idea was to look for resemblances between the remedies and what you wish to achieve in terms of the treatment.”

One of the most remarkable results, per Hanss et al., was the recovery of collagen peptides from hippopotamus teeth or bone, pointing to the global circulation of more exotic ingredients in the 16th century. Hippo teeth were said to cure kidney stones and “take away toothache,” and were even used to make dentures.

Hanss et al. also found that several of the proteins they found had antimicrobial functions, such as dermcidin (derived from human sweat glands), which kills E. coli and yeast infections like thrush. The samples also yielded insight into how Renaissance people’s bodies responded to the remedies. Traces of immunoglobulin,  lipocalin, and lysozyme are indicators of an active immune response, for instance.

Hanss is so pleased with these initial results that he hopes to launch a large-scale project to extend this interdisciplinary approach to other collections of medical manuals. He also hopes to further improve the dating methodology. “The ingredients for success are there,” said Hanss. “It’s not only that we found new answers to old questions, but we are now in a position to ask completely new questions.”

The American Historical Review, 2025. DOI: 10.1093/ahr/rhaf405 (About DOIs).