Found source of rotten egg/sulfur smell

Howdy...
I've noticed this sulfurous rotten egg smell from time to time in the last 2-3 months. It generally seemed to come from under the hood when the car was started cold. I was concerned since in the past that smell was associated with malfunctioning smog equipment or catalytic converters in other cars. I managed to track down the source of the odor today and luckily it has nothing to do with anything other than the windshield washer solution. Yep, that's right, for some reason the washer solution has deteriorated and gives off that truly nasty smell. I've been using concentrate that I bought from an auto parts store but just as soon as the washer reservoir is empty, I'm going back to that weak but odor-free blue stuff that sells by the gallon.