Irritants are typically thought of as chemical agents (for example phenol and capsaicin) but mechanical, thermal (heat), and radiative stimuli (for example ultraviolet light or ionising radiations) can also be irritants.
In Sydney Pollack's 1973 movie The Way We Were, Beekman Place symbolizes the Waspish cultural background of Hubbell Gardiner (Robert Redford's character) that is a continual irritant in his relationship with the Marxist Jew Katie Morosky (played by Barbra Streisand).