His chronicle of his trip, The naturalist on the River Amazons, became a bestseller when it was published in 1863.
Hot flashes and nausea are most commonly caused by hormonal imbalances in the body, most notably, by sex hormones. For women, a decrease in estrogen is often to blame, whereas in men, testosterone deficiency can create the problem. Sometimes, the symptoms occur for reasons not related to those hormones at all.
Hot flashes are mostly caused by the hormonal changes of menopause, but can also be affected by lifestyle and medications. A diminished level of estrogen has a direct effect on the hypothalamus, the part of the brain responsible for controlling your appetite, sleep cycles, sex hormones, and body temperature.