A lot of red rashes on the back in summer may be due to hives, eczema, folliculitis, etc. You can take oral anti-allergy drugs, use compound dexamethasone acetate cream, topical mupirocin ointment and so on. 1. Urticaria: due to allergies cause hives, resulting in a lot of red rashes on the back skin, sometimes accompanied by itching, you can take oral anti-allergy drugs, such as loratadine and so on. 2. Eczema: Due to the humid environment, a lot of red rashes appear on the skin of the back, you can use compound dexamethasone acetate cream and so on. 3. Folliculitis: Folliculitis caused by bacterial infection, causing a lot of red rashes on the back in summer, you can use mupirocin ointment and so on. If you have the above symptoms, you need to go to the hospital as soon as possible to clarify the cause, by the doctor for standardized treatment, do not blindly use their own medicine.