Fungal infections often cause itchy rashes and tiny blisters. It can be treated with anti fungal creams and ointments with a regular dose of antibiotics. It should not be touched or scraped with hands which may spread it to other parts.
An itchy rash with tiny blisters is most commonly a reaction to something. You could react to almost anything. Most common reactions are caused by household cleaners and products such as laundry soap or dryer sheets. Some people react to bath soaps and body washes. If you have changed any product you use at home, that could be the problem.