Put ordinary white bird's nest in a box full of swallow droppings. After about ten days, the bird's nest will be smoked red and turned into a blood swallow, or directly dyed with food pigment. The dyed "blood swallow" will be bright and even in color, sometimes dark red or big red, and then sold as "blood swallow". For many years, bird's nest has been regarded as a high-grade tonic, especially "blood swallow", which is a treasure among treasures. However, in August of 20 1 1 year, the sampling inspection by the industrial and commercial departments made Xueyan a news hotspot of social concern. First, it was found that the nitrite content in blood swallow exceeded the standard seriously, and the unqualified rate was as high as 100%. Then, the identity and source of blood swallows were questioned, and the sales of blood swallows on the market were stopped. The root of the "blood swallow" incident is the proliferation of smuggled bird's nest. Smuggling bird's nest does not need strict inspection by the inspection and quarantine department, thus evading the supervision of the government. The low illegal cost has led a large number of merchants to concoct "blood swallow" according to the traditional health concept of "eat what you want" in China. After the bird's nest was smuggled in, the merchants adopted the way of "selling dog meat by hanging sheep's head", a small amount of bird's nest was officially imported, and a large number of smuggled low-quality or fake bird's nest were sold. Consumers can't tell whether it is imported bird's nest or smuggled bird's nest, and the industrial and commercial departments can't supervise it, which eventually leads to a large number of bird's nest counterfeiting and selling, and a large number of "blood swallows" flood the market.