Hi,
From the photo, possible causes are:
1. Acute hand eczema due to internal sensitivity. Doctors call this condition pompholyx or vesicular hand eczema.
2. Contact dermatitis or acute eczema due to external contactants.
3. Id reaction or vesicular reaction due to a distant fungal infection.
4. Vesicular reaction due to an ongoing viral infection
As the potential causes are rather diverse, the appropriate treatment will really depend on the most likely cause. Do see your doctor for a thorough evaluation in order to determine the cause and to exclude something more serious.
Hope you recover soon!