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.
Chemotherapy and radiation therapy. These cancer therapies can induce menopause, causing symptoms such as hot flashes during or shortly after the course of treatment. The halt to menstruation (and fertility) is not always permanent following chemotherapy, so birth control measures may still be desired.