Tess M. Calloway is the pen name of Dr Theresa M. Callaghan, a Welsh author and cosmetic scientist who lives in Germany and still regards Wales as home.
During an international career spanning nearly forty years, Theresa has worked in cosmetic science, research and claims substantiation—the evidence behind the promises made about beauty products. She has also written educational books and articles examining how scientific findings become claims, and what can happen when the language moves beyond the evidence.
Fiction offers a different way to explore the human questions behind that work. How do people respond to commercial pressure? What makes someone challenge a powerful organisation—or remain silent? And how far will a person go to defend a decision they once believed was right?
These questions run through the Zoe Blaise Mysteries. Although her professional experience informs the stories, it is the characters—their loyalties, flaws, relationships and choices—that give them life.
Born and raised in Cardiff, Tess brings a lasting connection to Wales into her writing. Its streets, coastline and communities provide more than settings: they offer her characters a sense of belonging, even when their investigations take them far from home.
Tess is a member of the Society of Authors. She has spoken about her writing and scientific background on BBC Radio and in other media interviews. She also writes two LinkedIn newsletters: Beyond Cosmetic Claims, exploring science, evidence and communication, and Deadly Cosmetic Science, sharing the ideas and inspirations behind her fiction.
Why Tess M. Calloway?
Choosing a pen name gave my fiction an identity of its own, distinct from the scientific and educational work published under my professional name.
Tess is a familiar shortening of Theresa. Calloway echoes Callaghan while sounding different enough to mark that distinction.
It also carries a personal association with pebbly places: the shoreline at Aberaeron, where Zoe finds moments of peace, and Pebble, one of the characters who has become part of her world. Those connections made the name feel at home.
