It's a bacteria-fungi related infection that needs heat or steam-like treatment (low pressure 10mmpg)
Also they have scabbed up, it's not like they are open sores.
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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!