A lot of red dots on the back can be caused by insect bite dermatitis, allergic factors, acne and other factors. 1. Insect bite dermatitis: In summer, mosquitoes are more, when the back suffers from mosquito bites, it may induce insect bite dermatitis, which will make the back appear a lot of red dots, accompanied by intense itching. 2. Allergic factors: the presence of allergies, contact with allergenic substances, will also make the back appear a lot of red dots, accompanied by itching, redness, tingling and other symptoms, excessive scratching will also stimulate bacterial infection. 3. Acne: It may be related to genetic factors, excessive androgen levels and other factors, which can lead to acne in the back area, which can cause a lot of red dots on the back, and can lead to a lot of red dots on the back, which can lead to a lot of red dots on the back. A lot of red dots on the back, accompanied by other clinical manifestations, may be the existence of abnormal conditions, it is recommended to seek medical examination and treatment.