Hi and sorry about the itchy rash. Could be an allergy and perhaps due to the keflex, but could also be eczema. I have something like that on my legs. It starts out extremely itchy but if I scratch it (I don't do this any more) then it stops itching but becomes more red and like a bunch of individual small scabs and then it goes away. I also have it on my hands but there it starts as very tiny clear/colorless blisters that end of peeling or itching. It is dyshidrotic eczema. I now try keep the area dry and moisturized. For me Eucerin plus product, dry skin therapy hand cream. It is like a coating that is left after it dries and has been the only thing that works for me.It works on the legs and hands.
let me know if it works or what you find out. You may want to also post on the dermatology site.
Sorry to say sounds like herpes complex to me. go to a derma doctor for the skin he will know immediatly.
Shingles: (herpes zoster)
A painful, contagious rash caused by the chickenpox virus (varicella-zoster). Starts with itching, tingling, or pain in a certain area that later turns into a band, strip, or small area of rash. The rash turns into clusters of blisters. The blisters fill with fluid and then crust over. It takes 2 to 4 weeks for the blisters to heal, and they may leave scars. Some people only get a mild rash, and some do not get a rash at all.
Keflex can cause a blistering rash called Stevens-Johnson syndrome. Google it to find out more about it.