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Sand Flea Bites: What Actually Bit You at the Beach

By Andrew Rothaus, Founder ·

The "sand fleas" that bite American beachgoers are usually not fleas at all. They are biting midges (no-see-ums) or sand flies, and each has its own playbook. The true sand flea, the chigoe flea Tunga penetrans, is a tropical parasite of sandy climates, not a U.S. beach-blanket problem.

Coastal sand dunes with tall grass under a dramatic sky

Few bite names cause more confusion than "sand flea." The term gets applied to at least three different creatures, only one of which is a flea, and the right response depends entirely on which one you actually met. Here is how to tell, using what the CDC and state health guidance actually say.

What are "sand fleas," really?

On a U.S. beach, the itchy welts blamed on sand fleas usually come from biting midges, the insects the CDC describes as "tiny biting midges, sometimes called 'no-see-ums.'" The Illinois Department of Public Health puts them among the most serious pests "along the shores of oceans, lakes, ponds and rivers," biting day or night, and so small they pass through window screens. If you never saw what bit you and the welts arrived in clusters, this is the leading suspect; our no-see-um guide covers them in full.

The second candidate is the sand fly, a real insect with the beach in its name. Illinois DPH describes sand flies as long-legged, no more than 1/8 inch, hairy and brown to gray, with wings held in a "V" when at rest, and notes that most species feed on the blood of mammals, reptiles and amphibians at night. Night-biting is the tell.

The third, the true sand flea, is the one the name legally belongs to: the chigoe flea, Tunga penetrans, per the CDC. It is a genuinely different problem: the CDC's parasitology reference explains that mated females burrow into the skin of the host, causing a nodular swelling. Its territory, per the CDC, is tropical and subtropical regions, including Mexico to South America, the West Indies and Africa, in sandy climates including beaches, stables and farms. If you have not traveled to those regions, tungiasis is almost certainly not your diagnosis; if you have, and a bite has become a swelling nodule, that is a clinician conversation, not a blog-post fix.

Do sand flies carry disease?

In parts of the world, yes. Illinois DPH notes that certain sand fly species (Lutzomyia), in many parts of the world including southern Texas in the United States, are suspected of transmitting cutaneous leishmaniasis, a protozoan disease. The CDC's prevention guidance is built on one fact: "There are no vaccines or drugs to prevent leishmaniasis infection," so protecting yourself against sand fly bites is the prevention. For travelers to affected regions, that elevates bite prevention from comfort to health protection.

How do you prevent the bites?

The CDC's sand fly prevention guidance, in three moves:

  • Repellent, applied thoroughly. Use an EPA-registered insect repellent on exposed skin and under the ends of sleeves and pant legs. The CDC's leishmaniasis guidance notes that repellents containing DEET are generally the most effective for this use.
  • Indoors, screened or air-conditioned. The CDC advises staying in well-screened or air-conditioned areas when indoors in sand fly country.
  • For the beach no-see-um problem, the same tactics that work on biting midges apply, since they are usually the actual biter: a repellent whose label lists biting flies or no-see-ums, and moving air. Our no-see-um repellent guide has the full label-reading walkthrough.

Worth restating as a traveler's rule: within the United States, the beach-biter question is almost always midges versus sand flies, an itch-management problem. The tropical burrowing flea enters the picture with travel to the regions the CDC names, and its signature, per the CDC's reference, is not a welt but a nodular swelling as the burrowed female develops. Different organism, different response, different urgency.

How do you treat the bites you already have?

For the ordinary itchy welts, the CDC's bite-care steps: wash the bite and surrounding area with soap and water, and apply an ice pack for 10 minutes to reduce swelling and itching, reapplying as needed. And the standing rule: "Do not scratch bites. They can become infected."

The exception is the true sand flea scenario: a nodular swelling after barefoot time in tropical sandy places. That is tungiasis territory, and it belongs in front of a clinician.

Longsleeve is an EPA-registered picaridin lotion (EPA Reg. No. 101457-1). It repels mosquitoes and ticks for up to 14 hours, and its accepted federal label carries the claim "Repels biting flies, stable flies, black flies, gnats, chiggers, sand flies and Scottish biting midges (no see-ums) for up to 8 hours." It is fragrance-free, with nine disclosed ingredients. Of the 631 EPA-registered skin repellents in our Repellent Index, 47 carry a stated no-see-um protection time on their federal label.

Short answers

What do sand flea bites look like?

The clustered itchy welts American beachgoers call sand flea bites usually come from biting midges or sand flies, and they behave like other insect bites: bumps that itch and respond to the CDC's wash-ice-don't-scratch routine. A bite that becomes a swelling nodule after tropical travel is different: that pattern belongs to the true sand flea, Tunga penetrans, and warrants a clinician.

Are sand fleas and no-see-ums the same thing?

In everyday American usage, usually yes: the biters on the beach at dusk are typically biting midges, the insects called no-see-ums. The technical name "sand flea" belongs to a tropical burrowing flea that is a different organism entirely.

How do I tell midge bites from sand fly bites?

Timing is the most usable clue. Illinois DPH notes most sand fly species feed at night, while biting midges bite during the day or at night and mass along shorelines. In practice the response is the same: a repellent whose label covers biting flies, screens fine enough to matter, and the CDC's bite care for what already itches.

When do sand flies bite?

At night, mostly. Illinois DPH notes most sand fly species feed on blood at night, which distinguishes them from the day-and-night biting midges.

Should I worry about leishmaniasis at a U.S. beach?

The suspected U.S. transmission Illinois DPH names is in southern Texas, and the CDC's prevention guidance is aimed at people living in or visiting countries where leishmaniasis occurs. For travelers to those regions, sand fly bite prevention is the whole defense: there is no vaccine or preventive drug.

The usual suspect in full: no-see-ums, their bites, and the repellents that list them.

Sources

  1. Illinois Department of Public Health, Biting Flies. https://dph.illinois.gov/topics-services/environmental-health-protection/structural-pest-control/biting-flies.html
  2. CDC, Oropouche Puts Biting Midges Under the Microscope. https://www.cdc.gov/oropouche/stories/midges-under-the-microscope.html
  3. CDC, Preventing Leishmaniasis. https://www.cdc.gov/leishmaniasis/prevention/index.html
  4. CDC DPDx, Tungiasis. https://www.cdc.gov/dpdx/tungiasis/index.html
  5. CDC, About Mosquito Bites. https://www.cdc.gov/mosquitoes/about/about-mosquito-bites.html

Last reviewed 2026-08-26 · every claim on this page is sourced above