Due to the Sand Flea
Found in South America, The Caribbean and in sub-Saharan Africa.
Sand flea disease is the result of an intense inflammatory response against sand fleas embedded in the skin . Through its abdominal rear cone the parasite remains in contact with the environment . The opening in the skin is needed for copulation with male sand fleas, breathing, defecation and expelling eggs. After expulsion of all eggs the female sand flea dies and is discarded from the epidermis by tissue repair mechanisms . Although self limited, it is a debilitating disease in endemic areas due to the sequella of repeated and severe infection (PubMed).
Digging them out with unsterile tools in most of the world. Bad idea in the third world. Try topical Dimeticone (PubMed).