Based on the symptoms described, it seems like your 11-month-old daughter may have roséola. This condition is typically characterized by a high fever above 39 degrees. You can give her Benadryl every 6-8 hours and monitor for any other symptoms such as fever, runny nose, or loss of appetite. If there is no improvement after 48 hours of using Benadryl, or if more serious symptoms like lip inflammation or difficulty breathing occur, it is important to seek medical attention. You can also help soothe her skin with an unscented moisturizing cream.