First of all, I strongly recommend that you get this rash looked at by a professional. While I can offer my opinion, I cannot diagnose a condition like yours without actually seeing it.

The symptoms you describe are consistent with dyshidrotic eczematous dermatitis, a type of eczema that affects primarily the hands and feet. Many people with this condition have a history of allergies, asthma, or atopic eczema. Stress and climate (especially hot and humid) may contribute to outbreaks of the rash. Dyshidrotic eczema starts out with extreme itchiness and then the red bumps (vesicles) appear. Outbreaks can last a few weeks and reccur. Eventually, scaling and thickening of the skin can occur as can deep fissures (cracks) in the skin that may be prone to infection.

Other possible conditions that fit these symptoms include contact dermatitis, atopic dermatitis of hands, palar pustulosis, and scabies.

You should see a healthcare professional for proper diagnosis and treatment recommendations. Conventional medical treatments are aimed suppressing outbreaks, while a naturopath will help to identify and eliminate the cause of outbreaks. Good luck to you, and I hope this information is helpful.