Guanyan is a variety of bird's nest, which refers to the white bird's nest (white bird's nest) with better quality and complete cup shape. It is said that in ancient times, when offering bird's nests to dignitaries, clean and complete high-quality white birds would be selected. This is where the name Guan Yan comes from. "Blood Swallow", many people mistakenly believe that the swallows lack saliva and even vomit blood to build the nest, so they become blood swallows. In fact, the blood swallow is made of a kind of "brown-tailed swiftlet". The formation of the blood swallow is affected by the growth environment and water quality, and gradually oxidizes to form a red color. Because the output is small and things are rare, they have only become popular in recent years. In ancient times, official swallows were more valuable than blood swallows. Compared with the two, white swallow is rich in collagen and is beneficial to women's beauty care. It is easier to absorb, has a good taste, and is more convenient for making and stewing. Blood swallow is rich in minerals, with slightly higher contents of sodium, magnesium, copper, phosphorus and potassium. The key point is that many of the products on the market are artificially colored. If you don’t have enough identification ability, don’t buy them easily.