n. pl. al·ler·gies
1. A condition in which exposure to a substance, such as pollen, latex, animal dander, or a particular food or drug, causes an overreaction by the immune system that results in symptoms such as sneezing, itching, rash, and difficulty breathing or swallowing.
2. Informal An adverse sentiment; antipathy: an allergy to cocktail parties.
[German Allergie : Greek allos, other; see ALLO- + Greek ergon, action; see werg- in the Appendix of Indo-European roots.]
The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2018 by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Indo-European & Semitic Roots Appendices
Thousands of entries in the dictionary include etymologies that trace their origins back to reconstructed proto-languages. You can obtain more information about these forms in our online appendices:
The Indo-European appendix covers nearly half of the Indo-European roots that have left their mark on English words. A more complete treatment of Indo-European roots and the English words derived from them is available in our Dictionary of Indo-European Roots.