Itchy feet most commonly occur due to fungal infections. Fungal infections occur in feet or anywhere for that matter due to dampness. Usually, most people wear shoes with socks for almost 12 hours or so every day which causes dampness due to sweating, which percolates to the shoes as well. The next day, one may put on a fresh pair of socks but wear the same shoes again.
All these factors contribute to fungus growing and multiplying there. Poor hygiene and nylon socks are other factors which contribute to this problem and aggravate it.
People with immune depressed conditions like diabetes, HIV/Aids are prone to develop these infections early and in more severe form. Itching of the feet can also be due to allergy caused by the material in the shoes or socks or some body care product used locally. Eczema may occur in feet causing itching along with small eruptions.
Psoriasis is an itchy skin condition which can occur anywhere in the body including feet. There are silvery rashes along with itching. One may have infestation by hook worm (a parasite which can enter body through sole of bare feet) or any other parasite which may induce allergy and itching with or without rashes. The solution to this problem lies in improving hygiene of the feet. Feet should be kept always clean and dry. Ideally one should use a fresh pair of socks and the shoes must not be damp.
Nylon socks should be replaced by cotton ones. Using a dusting powder also helps in keeping feet dry. One can also use antifungal ointment or powder for few weeks for complete cure.