Collocations for irrational - adj.

appear, be, seem
become
consider sth, regard sth as, see sth as
dismiss sth as
He dismissed her fears as irrational.

completely, quite, totally, wholly
increasingly
somewhat
apparently (esp. BrE), seemingly
inherently
There was nothing inherently irrational in such a decision.

Irrational is used with these nouns:
belief, fear, hatred, jealousy, number, paranoia, prejudice