Most people thing car sickness is just one variety of motion sickness – the nausea and dizziness that attacks some travelers on airplanes, buses and cars. A few people with car sickness, however, may be reacting to auto exhaust fumes, molds and dust in the car air conditioner or the odor of new vinyl upholstery.

All those triggers can make an allergic auto traveler feel nauseated and sometimes dizzy or headachy. But even if they don't feel outright nausea, people with allergy induced car sickness can become irritable and easily annoyed by delays or others driver’s mistakes. And there are a host of other possible symptoms.

They may feel dopey and under-react to traffic situations. Perceptions may dull and reflexes slow down. Vision may blur. The driver may underestimate the time and distance needed to stop, or even fall asleep at the wheel. If you get sick, tired or irritable on car trips, take less heavily routes to avoid breathing heavily polluted air.

Above all, don't drive in the wake of a bus or diesel truck if you can possibly avoid it. When you stop to gas up, close the window while the service station attendant fills the tank. At self-service stations, wear a handkerchief over your nose and mouth to block out fumes while you fill your tank (be sure to remove the handkerchief when you approach the cashier, so he won’t mistake you for a robber!).

As we mentioned in Clearing the Air, allergic people should have their car air conditioners cleaned regularly before and during the hot weather season to eliminate mold and dust. As for sensitivity to vinyl car interiors and upholstery, you’ll be less likely to get sick if you buy a char that’s at least two years old. As vinyl ages, it gives off less odor.

Much of the fatigue that’s blamed on ”highway hypnosis” may actually be due to car related allergies. Following these precautions will not only help you arrive at your destination feeling well, but will also cut down your chances of a traffic accident along the way.