Itchy red bumps on plasters are mostly seen in allergy to plasters, which requires anti-allergy treatment. Generally speaking, the most common reason for itchy skin and red bumps after applying ointment is that the patient has an allergic reaction to the ingredients of the ointment, causing localized allergic dermatitis. After the allergic symptoms, the first thing to do is to remove the plaster immediately, rinse the plastered parts with water to remove the residual plaster ingredients on the skin. Then apply topical anti-allergic ointment, such as glycerite lotion and mometasone furoate cream, to treat the condition. Cold compresses can also be applied to relieve the itching. When the allergy symptoms are more serious, you need to take oral antihistamines such as cetirizine or loratadine to treat. It is best to go to the hospital for examination and treatment under the guidance of a doctor to avoid self-medication.