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Diabetes, psoriasis, hypothyroidism, contact dermatitis, atopic dermatitis and malnutrition should be ruled out first. Itchy feet with tiny white blisters could be eczema, fungal infection, dermatitis, contact allergy with allergens like soap, chemicals etc. If you itch between toes too, there are chances that it is scabies, fungal infection and sweat dermatitis. See if your feet come in contact with particular grass, shrubs, chemical etc. It can also be an infection under the skin or cellulitis. Do discuss this with a skin specialist as confirmed diagnosis is not possible on net. Take care!
I find so many older folk have a problem with malnutrition and drinking enough. Please be very vigilant to eat enough good food and maybe drink a glass of milk? It is a very prevalent problem.