Cracked heels are often the result of overly dry, thickened skin that splits under the pressure of standing and walking. For the afflicted, it happens in summer while wearing sandals, and during zero humidity winters. In many ways the problem of dry feet is the opposite of sweaty feet. It can be a really painful problem, especially as it gets worse.
This simple solution came from an old friend - Karyn in Oregon, who died recently in 1999. She had some crazy ideas about a lot of things. One idea was intimate uses for Krazy glue™ AKA Super glue™. She told me that hospitals use it in surgery sometimes, somewhat of a revelation to me. After a little research I found there is a chemical difference in the retail grade1 but I still felt I could still take her advice seriously. I knew it is relatively nontoxic in small amounts, but I'd always listened to word on the street to keep it away from body parts if I wanted them only attached in the right places. She on the other hand, used to use it for DIY skin repairs
It may sound a little Frankensteinian at first, but it works. Hold a crack closed, touch the applicator tip to the fissure and allow half a drop of the good stuff to flow along by capillary action thence sealing it. Allow a few minutes to dry. It is best if the split skin is cleaned, the glue is used sparingly and penetration is not deep enough to impede healing.
Feet are pretty much the ugly stepsisters of our extremities, so a little glue won't disfigure them and its an instant mechanical solution stopping thepain of walking on cracked feet. Anyhow, in a few days the glue wears off,
1 Medical grade cyanoacrylate contains butyl, iso-butyl or octyl esters These are more expensive to manufacture but have special properties useful in medicine, such as flexiblity, greater inertia and a lesser tendancy to produce heat while curing. In contrast, methyl esters are used in most retail grade cyanoacrylate because they are the cheapest to produce and also have the strongest bond.
NB With respect to thelady below. Use your discretion when considering this solution, as it is more along the lines of first aid. As a guy, sometimes in remote places hiking, I've found it useful to stop the problem getting worse. But I guess if your feet look like pack ice in summer you should refrain from lacquering them in glue. Still, in a pinch I'd rather take a drop of glue than a scalpel to my feet.
Medical disclaimer
This node is based on successful anecdotal evidence and lacks validation from a large sample size, animal testing or statistical analysis. Your own experience may vary based on geographical location, severity of the condition, skin micro-flora, individual biochemistry, species, habitat and unusual foot practices. If wealth and proximity allow regular visits to a podiatrist, consider this alternative.