I had these between my fingers for several years when I had a very stressful
job; it always appeared in late spring with the arrival of warm weather.  My
dermatologist prescribed hydrocortisone cream which did little to relieve
the itching and did not help to heal the lesions. The condition I had is
called dyshidrosis or dysidrotic eczema and there seems to be no agreement
on the cause which is listed as unknown, allergic, stress-related or linked
to fatigue. It is usually aggravated by humidity Transparent blisters
containing a watery substance form on the skin between fingers or toes; it
is accompanied by a burning sensation and itching.  In my case, it
seemed to be an allergic reaction aggravated by stress which depletes the
body's natural supply of antihistamines.   I was able to get rid of the
blisters in 24 hours with a homeopathic remedy which I will list below for
anyone who wants to try it.
If homeopathy wasn't available I would probably try clay or castor oil packs
and drink clay water which is made with 1 tsp. green clay powder in a large
glass of water--stirred with a wooden spoon--left overnight.  In the
morning, drink only the water and pour the remaining clay in your flower
pots.  This by the way is a very inexpensive way and easy way to remove
toxins, including heavy metals, from the body. It does take patience. In the
same vein I would try things to reduce acidity, like drinking kombucha,
taking a few drops of stabilized oxygen several times a day in a glass of
water, petting my cat, deep breathing, etc.

Hydrogen peroxide has given relief to some.  This treatment is described in
detail at http://www.geocities.com/vyera/dyshidrosis/main.html  There even
seems to be a forum for dyshidrosis.
**
The treatment for dyshidrosis from the homeopathic dictionary by Louis
Pommier:  Sulfur 4CH alternately with Rhus tox. 5CH (two grain
doses); Primula obconica 4CH  and Anagallis arvensis 4CH--two grains of each
every 24 hours. He recommends almond oil as a moisturizer.

I always have these on hand; I have never taken them more than two days
before the symptoms disappeared.

I hope this information helps.  I remember how painful it was.

Blessings,
Carlene