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.
Cold symptoms typically begin with a sore throat that may be mild or severe. After a day or two, the sore throat improves and nasal symptoms, such as congestion or a runny nose, appear. Nasal secretions begin as a thin and watery discharge, then develop into a thicker and darker discharge several days into the illness.
Flu and the common cold are different illnesses, although they may share some symptoms. You tend to feel much worse with flu, often being confined to bed for several days, whereas a cold will usually just make you feel under the weather. Flu and the cold are both caused by viruses, but completely different ones. There are hundreds of viruses that can cause colds, but only three strains that cause flu. People with flu normally feel very unwell for two or three days, and will continue to experience symptoms for around another five days.