Hi there! I’m a certified personal trainer! I can tell you there is no way to directly “burn fat.” However the most efficient way to lose weight is to eat less calories than you burn. If you consume more than you burn, it is most definitely impossible to lose weight. There is no magic pill or tea.
I looks at some articles about it and found that it does occur following a viral illness however it never said anything about Antihistamines so I still might be wrong. If it is wrong please comment the right answer for other people to see.