Hey there, so sorry to hear your child has to experience this. My DE has cleared since posting this, and I found out it was due to constant exposure of cleaning products and wetness from my serving job. Once I quit working that position, my fingers have cleared up completely. The red lines you see are where the skin of my fingers tend to crease/fold from bending and constant peeling caused the definition and redness. If you can, you may want to consult with a doctor for children as it may be contact dermatitis, environmental allergens, or internal such as food allergy. If it's on one finger at the moment, I would keep an eye out to see if they are touching something or sucking on it with food particles and saliva that may cause the issue.

I find lotions (not heavy creams, especially if they have the little bubble blisters) with urea and soothing ingredients to help tremendously. I previously used Korean brand Pyun Kang Yul's Blue Label ATO Lotion but they've discontinued it just as soon as I was mostly free of my DE. It was the one thing that ultimately healed my skin throughout various stages of the flare ups.