For years, Amy Farler, who designs transmission components for International Truck and Engine, suffered in silence. Once in a while, when an allergy-related sinus headache escalated into a full-blown migraine, she missed a day of work. But most of the time, she went to the office and quietly lived with the congestion and discomfort of her seasonal allergies. “Sometimes, it’s like you wouldn’t mind if your head rolled off your body,” says the 31-year-old engineer, who spends most of her day working with 3-D models on a computer screen. “You feel clogged up and hazy. The pressure makes you want to close your eyes. It’s hard to focus. You end up just muddling through.”

A version of this article appeared in the October 2004 issue of Harvard Business Review.