Probably a form of eczema called dyshidrotic eczema. Not allergic. Cause unknown. Treatment with prescription-strength cortisone creams helps if the symptoms are annoying enough to make the treatment worthwhile. Take a photo to show your doctor in case it gets milder before you go, and then check with the doctor in person. This condition is likely to come and go, so it's best to get a definitive diagnosis now so you'll know what to do in the future.
Best.
Dr. Rockoff