The itchy patches on the sides of your feet could certainly be caused by athlete's foot, also known as tinea pedis. Athlete's foot is a very commonly encountered problem in the primary care setting, and is caused by a superficial fungal infection of the skin. The infectious usually manifests as scaly, red, itchy skin, often between the toes or along the side/bottom borders of the feet. It is most often contracted by people walking barefoot in humid areas such as showers and locker rooms. Fortunately, there are over-the-counter topical antifungal medications (such as Lamisil) which work well to eradicate the infection.
The itchy patches could also be caused by other non-infectious processes, such as inflamed dry skin and various types of eczema
. If you have any concerns about your feet or notice that you start to develop any worsening rash or other alarming symptoms, make sure that you seek out the guidance of your primary care doctor