Yellow lower body hair can be a symptom of heredity, shrinkage of hair follicles, malnutrition, hypothyroidism and other factors. 1. Heredity: The color of human hair has a certain relationship with heredity. Some people are born with less melanin content, and their lower body hair may be yellow. 2. Hair follicle atrophy: Hair follicles shrink when the patient is older, and the follicles are unable to provide sufficient nutrients for the hair. Therefore, patients with atrophied hair follicles will have the symptom of yellow lower body hair. 3. Malnutrition: the lack of trace elements, minerals and vitamins in the patient’s body may lead to malnutrition, which may lead to changes in the color of body hair. Therefore, malnourished patients may appear lower body hair yellow phenomenon. 4. Hypothyroidism: Hypothyroidism can lead to a decrease in melanin in the patient’s body, resulting in yellow lower body hair. It is important to note that if physiological factors are excluded, the patient needs to go to the hospital in time and under the guidance of the doctor to carry out regular treatment.