The causes of large red bumps after scratching itchy skin include urticaria, measles, rubella, etc. Treatment includes oral medication and topical medication. 1. Urticaria: because of allergy to certain substances, the skin will have an allergic reaction, large bumps, then you can give oral levocetirizine, olopatadine and other antihistamine medication. Severe itching can be applied externally with glycerite lotion to relieve itching. 2. Measles: If the skin is infected by measles virus, this kind of virus will damage the skin and cause rash, there is no special treatment, pay attention to rest, do not contact others because of contagious, can give vitamin A and other drugs to assist in the treatment. 3. Rubella: If the rash is caused by rubella virus infection, then you can give ribavirin and other drugs for antiviral treatment. There may be other reasons for the phenomenon of large red bumps after scratching the itchy skin, please consult a doctor in a timely manner, the use of medication should be in accordance with the doctor’s instructions, do not blindly deal with their own, in order to avoid adverse reactions.