Because of allergies, the skin appears red, swollen, itchy symptoms, I thought to eat anti-allergy drugs can be good, did not expect the symptoms not only did not disappear, but more powerful. This morning, the experts reminded that this situation belongs to the allergic phenomenon of anti-allergy drugs, once appeared, to quickly stop using anti-allergy drugs. Anti-allergy drugs can also cause allergies, of which paracetamol and benadryl are the most common. There is a wide variety of chemical mediators that can participate in or cause allergic reactions, and the process of allergic reactions is extremely complex. When anti-allergic drugs can only block a certain part of the allergic reaction or the release of chemical mediators, but not the whole process, allergic reactions can still occur. If the patient’s symptoms increase instead of healing after taking anti-allergy drugs, drug allergy should be taken into consideration, instead of mistakenly thinking that the dosage is not enough, and it is very dangerous to increase the dosage without authorization. Allergies that occur after taking anti-allergy drugs are manifested as itchy skin, rash, diarrhea and abdominal pain, abnormal blood picture, etc. Serious cases are even life-threatening, and patients should go to the hospital in time. When the use of an anti-allergy drug is ineffective, consider switching to another anti-allergy drug with a different mechanism of action.