Sand Fleas and Flies

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Big ol’ barracuda (let him go, don’t eat them at this size due to ciguatera poisoning)

Recently, we were on the west coast of Florida doing some fishing. On the open ocean, luck was with us with some nice big fish, one of which was a large Spanish Mackerel that fed all four in our party. The rest of the time, we fished from the beach.

Heckuva nice mackerel

In the area where we were, there were large numbers of small biting flies on the sand. We were told by locals that they were “sand fleas”. Each bite left a small raised red welt; I easily had one hundred of them on exposed areas (and this was with the use of DEET-based insect repellent).

This episode got me thinking about the minor issues that an off-grid medic would likely encounter. Certainly, things could be worse. Biting insects often cause rashes and itching, but go away over time. Still, a group member’s work efficiency could be affected and, if the area is scratched, breaks in the skin may become infected. It’s always appropriate for the medic to recognize what threats exist that could cause medical problems, even the very small ones.


Sand flea (the real thing)

There’s some confusion about what is or isn’t a sand flea. What locals call a sand flea and what actually is one are two different things. A real sand flea (Emerita analoga) is a type of small crustacean that has an adult size of about 1 or 2 inches in size, depending on your location. Females are bigger than males. Also called a “mole crab”, it tends not to bite humans. I’ve often used them as bait for tasty crab-loving fish like pompano.

There are other creatures erroneously called sand fleas: “sand hoppers” (Orchestia agilis). These are crustaceans that look different from real sand fleas. They also appear very different from regular fleas, but have the same amazing jumping ability. They are much bigger (up to an inch) than your typical flea and look more like a tiny lobster. These are, like the mole crab, unlikely to bite.

There is, however, a tiny, yet nasty, flea that lives in the sand and does bite humans: the chigoe flea (Tunga penetrans). Females burrow into the skin of the feet and ankles. There, they grow to a centimeter in size and lay eggs. The appearance is that of a small black speck in the middle of a welt. Pressure from the swelling may cause serious discomfort.

Chigoe fleas can be removed with tweezers with care taken to avoid leaving the head under the skin. They may also be suffocated and killed on the skin’s surface with oil or petroleum jelly. As they leave a small open wound, antisepics and antibiotics are often given to treat infections in the area.


Chigoe fleas should not be confused with “chiggers”. Chiggers (Trombicula autumnalis) are tiny juvenile mites who live in tall weeds, grass, and wooded patches. These are reddish in color and barely visible to the naked eye. There are many species, but only a few bite as larvae, causing rashes and itching. Mites in this stage are what we recognize as chiggers. All chiggers are mites, but not all mites are chiggers.

Back to my tale of woe. It appears that none of the above qualified as the culprit for my particular ailment. It was clearly not a sand flea of any kind. It was a tiny flying bug but not a mosquito: a sandfly.


Although you’ll find a number of articles on mosquitoes and the diseases they carry at, I have yet to address sandflies. If you live in a warm coastal area in the southern United States, you probably are acquainted with them.

Sandflies aren’t just one species: The name stands for any flying, biting fly in sandy zones. Those in the Ceratopogonidae family are also called “biting midges”. Tiny enough to be considered, like chiggers, “no-see-ums”, they are responsible for small itchy red welts which last for up to two weeks.

Like mosquitoes, female sandflies suck the blood of humans and animals. For them, it’s a prerequisite for reproduction. They may, as in my case, attack in large numbers, biting on any areas of exposed skin.

Sandfly bites can cause small red bumps and blisters that may itch and swell. The effects may take hours to manifest, but last for days to weeks. Antiseptic and hydrocortisone lotions will help ease itching and prevent infections from developing. Some recommend diphyenhydramine (Benadryl), an ingredient in “Tylenol PM”. Be aware that, at higher doses (50 mg or more), drowsiness may occur.

Like mosquitoes, sandflies may (though rarely) transmit diseases in their bites. One of these is a parasitic illness called leishmaniasis. Victims develop skin ulcers which may take a year to heal.


–Wear DEET-based insect repellents; reapply every two hours and after swimming on the beach.

–Avoid the beach in the early morning, at dusk, after rainfall, or whenever the sky is overcast. Cooler temperatures are when sandflies and chigoe fleas are most active. Late morning and early afternoon are best.

–Windy days don’t allow sandflies to navigate very well and make it harder to bite.

–Keep moving: Sandflies will swarm you if you stay in one place.

–Use a lounge chair rather than lying on a towel. They’re more likely to bite lower legs and feet and avoid the face and neck. Deny them even that by covering lower legs and feet.

–Keep ground-floor windows and doors shut at night if you’re near the beach. Sandflies are often so small they fit through screens.


Although DEET didn’t prevent my becoming a victim of biting midges, it probably prevented the effects from being worse. DEET (N,N-diethyl-meta-toluamide)   was developed in 1946 but not widely used until 10-20 years later, when the insecticide DDT was found to have negative environmental impact. The Environmental Protection Agency (EPA) last reviewed DEET in 2014 and believes it is safe when used as directed.

DEET doesn’t kill biting insects like mosquitoes or sandflies, but the chemicals in it affects neurons and receptors located on antennae and mouth-parts to repel them.

The EPA states that there is no age restriction regarding DEET usage. Products containing DEET can be used on children but I suggest avoiding the highest concentrated products. Irritation may occur.

I wondered about expiration dates, but most products containing DEET don’t have one listed on the container. This suggest they are, at least, long lasting. Over time, however, effectiveness may decrease.

Those preferring a natural alternative might consider lemon eucalyptus oil (also EPA-approved). Other natural products used include oatmeal baths and aloe vera.

It’s important to apply insect repellent correctly. If you use a spray, shake first, then hold 6-8 inches from skin and clothing and spread evenly. Some repellents can cause eye irritation, so spray onto your hands first, then apply to the face.

Off-grid medics must recognize bites that may be minor but can cause infection if not caught early. That way, a bump on the road doesn’t become the end of the road for their patient.

Joe Alton MD

Joe Alton MD

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