What is causing non pus filled blisters on the bottom and sides of my 1 year old grandsons feet?

Dyshidrotic Eczema: Dyshidrotic eczema is a type of eczema (dermatitis) of unknown cause that is characterized by a pruritic vesicular eruption on the fingers, palms, and soles. The condition affects teenagers and adults and may be acute, recurrent, or chronic. A more appropriate term for this vesicular eruption is pompholyx, which means bubble. The clinical course of dyshidrotic eczema can be mild or severe.