A lot of small red dots on the arms may be due to folliculitis, keratosis pilaris and other reasons. 1. Folliculitis: Folliculitis is often associated with bacterial infection. When the skin follicles in the arm area have an inflammatory reaction due to bacterial infection, it will lead to the appearance of red papules centered on the hair follicles in the skin in that area, which will make a lot of small red dots appear on the arm. 2. Keratosis pilaris: a chronic follicular keratosis pilaris. Heredity, vitamin A deficiency, endocrine and other factors may lead to the formation of perifollicular keratosis. This leads to small papules that are the same color as the skin or light red on the outside of the upper arm and the front side of the thighs, which can be manifested as a lot of small red dots on the arm. 3. Other: diseases such as cherry angioma may also lead to the appearance of red dots on the arms. When there are a lot of small red dots on the arm, it is recommended to go to the hospital in time for consultation and examination, and after clarifying the cause of the disease, actively carry out targeted treatment.