Japanese Apricot (Prunus mume, also known as ume or umeboshi when pickled) has a long history of use in East Asian traditional medicine, including Japanese Kampo and Chinese medicine. It is commonly employed as a remedy for various ailments, especially for digestive issues, fatigue, and to "clear heat," which can be interpreted as addressing feverish conditions, including colds with fever. Traditional texts often describe ume as having properties that help detoxify the body and support the immune system, thus providing relief during febrile illnesses.

However, the scientific evidence supporting the use of Japanese Apricot specifically for treating colds with fever is limited. Some modern studies have explored the fruit’s antioxidant and antimicrobial properties, suggesting it may help inhibit certain bacteria and viruses and modulate the immune response. These studies, though, are preliminary and do not provide robust clinical data directly linking ume consumption to faster recovery or symptom improvement in febrile colds. Therefore, while traditional use is well-documented and there are some plausible mechanisms suggested in laboratory studies, high-quality clinical trials are lacking.

In summary, the use of Japanese Apricot for colds with fever is primarily justified by traditional usage, with some low-level scientific support for general immunomodulatory effects, but not enough to recommend it as a proven treatment.