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.
There may be many different causes of hot flashes, but hormones are always at the root of the problem. When estrogen reaches low levels, it affects the hypothalamus in the brain. The hypothalamus manages several body functions, including sleep, regulation of sex hormones and the temperature within your body.