First of all, if the red bumps on the patient’s body have appeared for a long time and are mainly located on the back and forehead, acne may have occurred, which is a chronic inflammation of the sebaceous glands of hair follicles. This may be a case of skin allergy. Some patients may have skin allergies without significant itching or tingling, but other patients may have red bumps due to bacterial or fungal infections, such as mild folliculitis or Malassezia folliculitis, which may also cause painless red bumps. It is difficult to make a definitive diagnosis without an interview, so it is best for patients to visit the dermatology department of a regular hospital.