If your baby has redness and swelling around the arm after the DPT vaccination, it is most likely due to poor absorption and local infection. Generally speaking, you should pay attention to the cleanliness of the injection site after the vaccination, do not take a bath or touch water for a short time, and wear cotton, clean and soft clothes to avoid excessive friction. You can apply hot compresses to the area or use potato slices on the hard areas. These measures can help accelerate the absorption and promote the reduction of swelling. When once the redness and swelling around the injection site is found, you can use 75% alcohol for local disinfection, change your baby to loose clothing, and after the vaccination you can give your baby more warm water to observe the change in body temperature, and eat a light, nutritious diet with appropriate fresh vegetables and fruits.