'pseudoallergic' is formed from the combining elements 'pseudo-' (from Greek 'pseudes', meaning 'false') + 'allergic' (from 'allergy', itself coined from Greek roots 'allos' 'other' + 'ergon' 'work' via German 'Allergie').

'allergy' was coined in the early 20th century (Clemens von Pirquet, 1906) from Greek elements and German medical usage; the prefix 'pseudo-' has been attached in medical literature later in the 20th century to indicate 'allergy‑like but not true allergy', producing 'pseudoallergic' as a clinical descriptor.

Originally the components conveyed 'false' + 'other/response', and over time the compound came to mean 'an allergy‑like reaction that is not mediated by the immune system' rather than a deliberately 'false' phenomenon.