How to accurately determine the difference between urticaria and rubella? Urticaria and rubella are both common skin diseases that share many similarities and can easily be confused. Therefore, if you want to accurately determine the difference between urticaria and rubella, you need to pay attention to the following aspects. 1. In terms of etiology, the appearance of urticaria is usually due to the skin tissue releasing a large amount of histamine after contact with allergens or being irritated, causing blood vessels to dilate and intravascular fluid to leak out, thus forming papules, blisters and other symptoms on the skin. Rubella is an acute infectious disease caused by a virus. Causes of urticaria