The child has a swollen arm with hard lumps from the DPT vaccine can be treated with hot compresses and other treatments, and if there is aggravation, you need to consult a doctor in time. The main reason for this is that the child’s arm is swollen and lumpy from the DPT vaccine is due to allergy. Some of the components of the vaccine can lead to an allergic reaction, especially in the upper arm area after subcutaneous injection, similar performance is a normal adverse reaction range. You can use a hot towel to apply localized warm compresses, which can generally provide relief. However, if the relief is not obvious, or even acute exacerbation, or localized pain is obvious, accompanied by fluctuating sensation, etc., then we need to consult a doctor in time. Under the guidance of the doctor to carry out blood routine, ultrasound and other tests, to clarify the specific causes of the disease and then take symptomatic treatment.