There are two reasons for the formation of redness: 1, blood vessel expansion to form redness; 2, skin thinning redness can be seen with the naked eye. The reason is divided into normal and abnormal two kinds, normal, such as some people’s faces from childhood can see obvious red blood, is hereditary, born with thin skin, without any discomfort. Often referred to as plateau red, northwestern or northern people on both sides of the cheekbones red, is living in the plateau for a long time, hemoglobin content is not enough, caused by the expansion of blood vessels is also normal. It is also normal for a girl to blush when she sees her favorite boy, and it is transient. Abnormal situation is because the skin becomes sensitive, the stratum corneum becomes thin, the reactivity of blood vessels increases, redness is more likely to appear, this redness will generally be combined with other symptoms, such as skin fever, itching, flushing, skin is particularly sensitive, dry and flaky, there is exudate, and even combined with pimples, acne, belong to the category of sensitive skin, this kind of redness needs to be treated.