Not yet investigated
What we have so far
Terpinen-4-ol is the active; oxidised old oil is the allergen. The 2007 report tying it to gynaecomastia has never been cleanly replicated.
This star is on the map because the show intends to take the question apart properly — the trials, how it is actually tested, whether the thing sold is the thing studied. That work is not done yet, and nothing here should be read as a conclusion. When the investigation is published it will appear on this page.