How your dog knows when you are sick?

In recent years, organizations all over the world have looked to train dogs to detect medical conditions in humans. Numerous studies have shown that trained dogs can detect many kinds of disease — including lung, breast, ovarian, bladder, and prostate cancers, and possibly Covid-19 — simply through smell. The human body apparently gives off a distinct odour as a result of specific chemicals being released into the bloodstream before or perhaps during a seizure or heart attack. Your dog can smell and associate this change of your normal smell and understand you are in impending danger. Can dogs detect health problems in humans?