The black stuff that comes out of a jigger lesion is a combination of the flea’s body parts, its feces, dried blood, and eggs. The visible black dot at the center of the lesion is the rear end of the sand flea itself, which stays exposed to the surface while the rest of the flea is buried in your skin. As the flea feeds, grows, and eventually dies, the dark material becomes more prominent and can include decaying flea tissue that your skin gradually pushes out.
What Creates the Black Dot
A jigger (Tunga penetrans) is a tiny sand flea that burrows into the outer layer of skin, usually on the feet. It digs in headfirst, leaving only its back end poking out through a small opening. That exposed rear end is the black dot you see at the center of a white, raised bump. The opening serves two purposes for the flea: it breathes through it and expels eggs from it.
Over the course of about two weeks, a female flea ejects roughly 100 eggs through that tiny hole. The eggs are whitish and drop onto the ground, so they’re not what most people notice. What catches attention is the dark, sometimes paste-like material that also comes out of the lesion, which is a mix of the flea’s waste (called frass), digested blood, and skin debris. As the flea gorges on blood and swells with developing eggs, the black dot visibly grows larger.
What Happens as the Flea Dies
After burrowing in, the flea expands over about seven days to roughly the size of a pea through a process called neosomy, where its abdomen balloons to accommodate hundreds of developing eggs. The female typically lives four to six weeks embedded in the skin. Once it finishes releasing eggs, it dies in place.
After death, the flea’s body darkens entirely, turning from a whitish disc with a central dark point to a completely black mass. Your skin then slowly pushes the dead flea out, leaving behind a circular crater-like lesion often filled with blackened remains. This is when people tend to see the most dramatic “black stuff,” as the decomposing flea body, residual waste, and dried blood all get expelled together. The whole process, from penetration to the flea being sloughed off, takes several weeks.
Why the Lesion Gets Infected
That small opening in your skin is essentially an open wound for the entire time the flea is alive, which makes bacterial infection extremely common. A study of tungiasis patients in western Kenya found that 69% had at least one type of bacteria colonizing their lesions, while 31% had multiple bacterial strains present simultaneously. The most common were Staphylococcus species, the same bacteria responsible for many skin infections, but researchers also identified a range of other organisms including some associated with soil and fecal contamination.
The bacterium that causes tetanus, Clostridium tetani, has also been found in jigger lesions. This makes sense given that jiggers are picked up from contaminated soil, often in areas where people walk barefoot. The black material coming from an infected lesion can look darker, smell worse, or contain pus compared to an uncomplicated infestation. If the area around the lesion becomes hot, swollen, or increasingly painful, bacterial infection is the likely cause.
Where Jiggers Are Most Common
Tungiasis affects people in roughly 88 countries, concentrated in tropical regions of sub-Saharan Africa, Central and South America, and the Caribbean. Over a billion people live in areas where the disease is prevalent. In Africa, prevalence rates vary dramatically: a systematic review found rates as high as 53% in parts of Cameroon, 39% in Kenya, and 38% in Ethiopia. The disease hits hardest in communities where people walk barefoot on sandy or dusty soil, particularly during hot, dry seasons when flea populations peak.
How Jiggers Are Removed and Treated
The most common approach worldwide is manual extraction, where the flea is carefully dug out using a sterile needle or similar tool. This works but comes with real downsides: it’s painful, and if the flea breaks apart during removal, leftover fragments trigger intense inflammation. Using unsterile instruments, which is common in resource-limited settings, raises the risk of secondary infection significantly.
The World Health Organization recommends a silicone-based oil (a two-component dimeticone product) as the preferred treatment. Applied to the lesion, it suffocates the embedded flea. In a clinical trial comparing this approach to a sodium carbonate solution, the dimeticone killed 87% of embedded fleas within seven days, compared to 64% for the alternative. Once the flea is dead, the body can work to expel it naturally, and the dark material gradually clears as the skin heals over the following weeks.
If you’ve traveled to an affected region and notice a small white bump with a black center on your foot, particularly between the toes, around the toenails, or on the sole, that black spot is almost certainly a burrowed sand flea. The sooner it’s addressed, the less time bacteria have to colonize the wound and the less material accumulates in the lesion.