Your toddler is suddenly scratching at the dinner table, on the playground and while in your arms at story time. If no underlying physical causes are responsible for the itching, the most likely reason is that the itching has become habitual. You'll have to get creative to help her break the habit.
Two reasons are generally responsible for children to begin habitual scratching. The first is that the behavior has become a habit after months or years of scratching their way through bouts of eczema. After all of this time, and even after you've gotten the eczema under control, the need to scratch is not in response to a physical stimulus, but rather an unconscious, habitual action. The other reason is the same reason other kids twirl their hair, fidget with their fingers or suck their thumbs -- it is one of those little quirks that kids and adults adopt for a variety of reasons, including stress and fatigue.
Itching behavior might seem harmless enough at first, but the severity of the problem can increase rapidly. If your child scratches persistently, a rash can develop. This is even more serious if you've recently gotten the child's eczema under control because it can cause the skin condition to flare up again, giving the child a real reason to feel the need to scratch. If the scratching begins to break the skin, infections can follow. Just like any other open wound, it is susceptible to bacteria and must be cared for with antibacterial ointments. If that happens, consult your health care practitioner for further medical care.
If your toddler is younger, you can help prevent the scratching from causing injury by covering her hands with scratch mittens. However, even younger toddlers might be quick to figure out how to take them off. If the weather permits, keep as much skin covered as possible. Even at bedtime, dress your child in footed pajamas with long sleeves to prevent skin damage during the night. For older children, help them to change the itching behavior by reminding her each time she starts to scratch. You can use a keyword or phrase to keep the reminder discreet if there's any possibility your child will be embarrassed. If all else fails, tell your child to rub, not scratch. The gentler action won't break the habit, but it will not cause any damage to her skin.
Sometimes the best way to help your child break the itching habit is to provide her with something else to keep her fingers busy. Give her craft chenille sticks to fidget with when she's listening to you read a story, give her non-toxic modeling clay to mold during car rides, encourage her to draw during playtime or work on her musician's skills on her toy keyboard. All of these actions keep her fingers engaged in other activities, thus lessening the unconscious desire to scratch. Keep a variety of different fidget tools on hand as well for times of stress and other triggers that seem to exacerbate the itching behavior.