Athlete's Foot, properly known as Tinea Pedis, can cause itching and burning under the foot, and sometimes redness of the skin, peeling and blisters (pustular tinea pedis). Treatment can usually relieve symptoms significantly within 1-2 weeks, but as a general rule, you're best off treating the skin infection consistently for 1 month, and then for a week of each month for a further 12 months if you have had athlete's foot for a while. 

This is because the skin renews every two weeks, so treating for one month will mean you clear the skin for one whole skin cycle, and then by treating for one week of each month, you prevent re-infection. 

Lamisil Once is a particularly useful product as when applied to a dry foot, one application will treat the foot for a whole week, meaning that you only need to do the treatment once weekly, rather than once a day - like the other Lamisil products. 

Other antifungals that are not part of the Lamisil range require treatments to be applied twice daily, unless instructed otherwise.