At an early age, he and his sister Helena Rajchman became keenly aware of the social injustices in their "country" (Poland did not officially exist at the time) and were involved as teenagers in teaching young workers.

Rajchman did his post-doctoral studies at the Pasteur Institute in Paris, then briefly returned to Kraków (he was banned from going to the Russian-occupied part of Poland), before being named to a prominent bacteriological laboratory in London.

Rajchman travelled extensively to fulfill his mandate and notably became fascinated by the need for a quarantine and public health system in China: as such he became adviser to the Chinese government and became intimate with the Chang Kai-shek family and especially with T.V.

In 1924, together with Arthur Sweetser, the League of Nations' Press Officer, and the Institut Jean-Jacques Rousseau educators Adolphe Ferrière and Paul Meyhoffer, he founded the International School of Geneva, the first of its kind in the world.

Sikorski named him to be in charge of Polish refugees and gave him a letter to take to President Roosevelt asking for US help; he also issued Rajchman a diplomatic passport which was what allowed him to flee France through Spain and Portugal and eventually reach Washington DC.

Towards the end of the war, UNRRA commissioned him to write a report on how to deal with the drastic state of health conditions once Europe would be freed, notably a typhus epidemic was feared.

[citation needed] When UNRRA announced at a UN meeting in Geneva that it would be putting an end to its relief efforts, Rajchman stood up before the assembly and called for the creation of a Fund dedicated to helping children throughout the world.

In the context of the nascent Cold War and Stalinism in Soviet block countries, Rajchman was subpoenaed in the McCarthy period: he abruptly left for France and never returned to the United States.