In Jewish custom, Passover (Pesah) is a time of house cleaning as well. The very solemn holiday is meant to mark the exodus of the Jews from Egypt and takes place two weeks after the Jewish new year has come. Because the slaves in Egypt (including the Jews) were fed unleavened bread (bread without yeast, called "matzah" in Hebrew), the Jews adopted the bread as a symbolic reminder of the subjugation they overcame [source: History Channel]. It's a humble bread, and during Passover, keeping leavened bread (chametz), which is any bread made with yeast, is considered arrogant and ungrateful.
In fact, keeping leavened bread in the home during Passover is considered such an affront in Jewish culture that even overlooked crumbs count. To combat inadvertently insulting God, Jews scour their homes before Passover to ensure they didn't miss any bread. Since Passover comes around April, many people consider this custom as the origin of spring cleaning.
There's yet another culture, the Chinese, in the running as the originator of spring cleaning. Like Iranians, the Chinese clean their homes in anticipation of the new year (which occurs shortly after the Western new year). The Chinese sweep their floors and clean their homes to rid of bad luck and misfortune that may have accumulated during the previous year. Once the house is a clean slate, the Chinese welcome good fortune by observing a prohibition against sweeping for the few days following the new year in order to prevent sweeping away any good fortune that came with the turn of the year [source: Parker-Pope].
Ultimately, spring cleaning may have more to do with simple biology. During winter, we're exposed to less sunlight due to shorter, often dreary days. With a lack of exposure to light, the pineal gland produces melatonin -- a hormone that produces sleepiness in humans. Conversely, when we're exposed to sunlight, our bodies produce much less melatonin. It's possible that we spring clean simply because we wake up from a winter long melatonin-induced stupor and find more energy as the days grow longer when spring arrives. After all, it's easy to allow a house to get a little gross around the edges when you're sleepy.