Environmental Causes
There has not been extensive research into environmental causes of hyperosmia, but there are some theories of some possible causes. In a study by Atianjoh et al., it has been found that amphetamines decrease levels of dopamine in the olfactory bulbs of rodents. On this basis, it has been hypothesized that amphetamine use may cause hyperosmia in rodents and humans, but further research is still needed. This theory is supported indirectly by the fact that patients with Parkinson’s Disease have an increase in dopaminergic cells in the olfactory bulb and usually exhibit hyposmia. Anecdotal support for the idea that amphetamines may cause hyperosmia comes from Oliver Sacks’ account of a patient with a heightened sense of smell after taking amphetamines. It has also been observed that the inhalation of hydrocarbons can cause hyperosmia, most likely due to destruction of dopaminergic neurons in the olfactory bulb. Methotrexate, administered in the treatment of psoriasis, has been known to cause hyperosmia, and is more likely to do so in patients with a history of migraines. However, this is only an observation and not part of a study; therefore it has not yet been verified.
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