Barefeet lead to summertime injuries.

Even though I am a Podiatrist, I have to admit... "I hate shoes." When I was a child through my early adult years, I despised wearing shoes. But that is one of the ways I found Podiatry and became a Podiatrist... to many foot complications from years of not wearing shoes.
It is a natural tendency during the warmer months for children, teenagers and adults to not want to wear shoes. "My feet get to hot," I hear all the time when someone comes into my office or I see someone in the emergency room from an injury related to going barefooted. Here are just a few things I see as a result:
1: Athletes foot which leads to hard to treat fungal nails. If you are in areas where there is a lot of moisture (communal bathrooms, pools, ponds, lakes, oceans) and walk around barefooted you set yourself up for athletes foot or tinea pedis. I see people in my office with other complaints and notice they have tinea and 90% of these presentations are asymptomatic (no itching, redness, or weeping between toes).
2: Puncture wounds. Nails, broken glass, thorns, pieces of metal (I took a sewing needle out of a ladies foot just the other day) can lead to infections and scaring. Some of these foreign bodies are hard to see on x-ray so a large incision must be made on the bottom or top of the foot to find it. Also, it is very important that if you do step on something, go to the ER or your family doctor for a tetanus shot.
3: Lacerations and crush injuries. I see most of these from objects falling on the foot such as bottles from coolers and cans from groceries. If you lacerate your foot, don't use hydrogen peroxide as this kills good tissue. WASH, WASH, WASH. Wash the area with mild soapy water and rinse it under running water thoroughly.
4: Fractures and ripped off toenails. This comes mainly from stubbing the toe or catching the nail on the edge of a step. Fractures may require surgery and the toenail may have to be totally removed. Some nail injuries can cause damage to the nail matrix (where the nail grows from) leading to a deformed nail that does not grow straight or a portion stop growing altogether.
So even though your feet may be 'hot' wearing shoes, I advise protecting them as much as possible to avoid injuries.

"The journey of life is taken one step at a time... none of them should be painful." G.M. Barclay, DPM, AACFAS