The Second World War forced the company to relocate from Paris to Vichy, where several other pharmaceutical companies were already installed. The Vichy Regime took an interest in the company, and attempted to despoil Jewish stakeholders. However, two of the main stakeholders were from Switzerland, and Swiss ambassador Walter Stucki managed to first delay the ploy, and eventually to derail it entirely.
Business slowed down for Tho-Radia during the war, but from 1948 it gathered momentum again, as Alexis Moussalli and chemist Pierre Corniou developed further products such as skincare beauty milk, perfume and lipstick. At its zenith, the company had between 80 and 90 employees.