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Watch out for air-con flu … A flu shot won't protect you against one of the summer's most annoying illnesses -- a flu-like virus that you can get by constantly going from hot streets to freezing air conditioning. If you doubt that it's real, a 2004 study found that being in air conditioning can cause health problems, especially if the units aren't well maintained. Symptoms may include headaches, dry cough, dizziness, nausea, trouble concentrating, fatigue and sensitivity to odor. And, of course, that annoying summertime sneeze.