What do you suggest if my child is 14 months old she has a rash from head to toe?

Take her to a doctor: If the rash bothers her, I would suggest that she be seen by a doctor. There are so many reasons that a 14 mo old girl would have a rash. The list includes infection ( both viral, bacterial), inflammatory disease such as rheumatoid arthritis, allergy (such as hives), drug rash (such as amoxicillin), contact dermatitis such as poison ivy, skin disease such as eczema, etc. The treatment differs.