You may be allergic to or have a high sensitivity to the CFCs in the air conditioner ... freon may be the culprit.

what's CFC ?

A chlorofluorocarbon (CFC) is an organic compound that contains only carbon, chlorine, and fluorine, produced as a volatile derivative of methane, ethane, and propane. They are also commonly known by the DuPont brand name Freon. The most common representative is dichlorodifluoromethane (R-12 or Freon-12). Many CFCs have been widely used as refrigerants, propellants (in aerosol applications), and solvents. Because CFCs contribute to ozone depletion in the upper atmosphere, the manufacture of such compounds has been phased out under the Montreal Protocol, and they are being replaced with other products such as HFCs[1] (e.g., R-410A), hydrocarbons,[2] and CO2. However, such products[3] are similar in effect as pollutants.from wikedpedia
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