immediate allergy

[ĭ-mēdē-ĭt]
n.
  1. Hypersensitivity that becomes evident within seconds or minutes after contact with an antigen, reaches its peak within an hour or so, then recedes.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.