What does the word allergy mean?

The origin of the word ‘allergy’ comes from the Classical Greek word ‘allos’, then the German word ‘allergie’. It is a noun with the following meanings:

• A hypersensitivity to a specific substance (such as food, pollen, dust etc.) or condition (as heat or cold) which in similar amounts or degrees is harmless to most people: it is manifested as a physiological disorder
• A strong aversion