Hello, I can understand your concern for sudden occurrence of red blotches on face and neck of your child. These type of rashes are most commonly normal process in most of the children. Parents are often get confused with urticaria or allergic reaction. Rashes are quite common condition caused by bursting of allergy producing cells known as mast cells due to certain aggravating factors present in the environment. As the chemical inside them is released it produces a rash which you have mentioned. All of these allergic rashes are quite bothersome in children and are always accompanied with itching of mild to moderate nature. In your baby there is no itching so it cannot be an allergic rash. You can apply a simple moisturizing cream over the affected area at the time of occurrence. Protect her from extremes of weather conditions. Take care.