"Following each heavy rain, my residential crawlspace was filled with several inches of water. Generally this would evaporate after a few days. However, during the year with the highest number of vertigo episodes, the water was not draining. There was also a foul odor of rotten eggs I attempted to mask with air freshener, open boxes of baking soda, and moisture absorbing crystals. Perhaps it didn't bother me as much because (a) I was more concerned with dizziness and (b) certain gases neutralize the sense of smell during prolonged exposure."
These are the effects of exposure to various gases according to WDHS: "Exposure to low levels of hydrogen sulfide causes irritation of the eyes and respiratory tract. Other symptoms include nervousness, dizziness, nausea, headache, and drowsiness. This gas smells like rotten eggs, even at extremely low concentrations. Exposure to high concentrations can interfere with the sense of smell, making this warning signal unreliable... High concentrations of methane in enclosed areas can lead to suffocation as large amounts of methane will decrease the amount of oxygen in the air. The effects of oxygen defficiency include headache, nausea, dizziness and unconsciousness." 
"Remedies for the water accumulation were pursued. A deteriorated sewer pipe was discovered. The plumber said that based on its appearance, the pipe had been slowly leaking for years before the hole expanded and released a significant amount of sewage beneath the house. Combined with the gutter downspout drainage problem, a cesspool of stagnate toxic waste had accumulated. Wiring in the crawlspace even had to be rerouted to the attic."
"With the allergic sensitivity to mold and mildew, my home was, quite literally, making me sick.  Sewage containing hydrogen sulfide, ammonia, methane, carbon dioxide, sulfur dioxide and nitrous oxides in addition to household cleaning fluids like chlorine bleach combined to form toxic gases. During the years when I averaged five vertiginous episodes, the pipe's hole was small and exposure was mild. The bodily cleanses helped to remove some toxins but the most significant remedy was water evaporation in the crawlspace."
"After the floodgates of sewage were opened and evaporation ceased, intestinal cleanses were ineffective. Medications only added to the toxicity. In the end, installing a downspout that diverted excess water away from the house, replacing sewage pipes, and drying out the crawlspace eliminated the physical symptoms."
"With a combination of anger and relief I see the reward of persistence. Following 10 years of vertigo there have been no episodes during the past 12 months since the drainage problem was corrected. And I am happy to say I am no longer taking any medication for migraines or any related ailments."
Oddly enough, if the fictitious Gregory House were diagnosing the condition, he would have discovered the cause immediately. As viewers of the show realize, he routinely attempts to rule out environmental causes.
Tags: case study, otolaryngologist, relief from dizziness, unlikely cure for vertigo