I have a small crack under one of my toes. this usually happens every summer when wearing flip fops. its quite painful. are there any otc products i can use on it?

Tinea Pedis: Cracks of the skin between or under toes usually indicates that there is a fungal component. Try using an athletes foot spray containing terbinafine and scrubbing your feet (especially the toe region with a brush). You can use the spray on your shoes too to eradicate the fungus there as well. After the solution is well absorbed, try massaging your feet with an emollient lotion.