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PubMed This is a summary of 15 peer-reviewed journal articles Updated
Infectious Disease · Loiasis

What Are Calabar Swellings? Symptoms & Causes of Loiasis

At a Glance

Calabar swellings are temporary, migrating skin swellings caused by an allergic reaction to the adult Loa loa parasite moving beneath the skin. They commonly appear on the limbs and face, causing intense itching and redness, and require prescription antiparasitic treatment to cure.

In this answer

3 sections

01

What Causes Calabar Swellings?

02

Where Do They Occur and What Do They Feel Like?

03

How Long Do They Last and What Should You Do?

Random, traveling swellings under the skin are a hallmark symptom of loiasis (Loa loa infection) known as Calabar swellings [1][2]. These swellings are temporary and migratory, meaning they appear suddenly in one area, last for a short time, and then disappear, only to potentially reappear in a different location later [1][3]. While it is completely normal to feel distressed by the realization that a parasite is moving under your skin, understanding why these swellings happen is the first step toward getting appropriate care.

What Causes Calabar Swellings?

These swellings are not caused by the physical size of the worm stretching your skin. Instead, they are an allergic reaction—specifically, a localized angioedema (swelling under the skin)—to the adult Loa loa worm as it moves through your subcutaneous tissue (the layer of fat and connective tissue just beneath your skin) [4][5].

As the adult worm migrates, it releases proteins and metabolic antigens. Your immune system detects these foreign substances and mounts a defense, triggering localized inflammation and fluid leakage from nearby blood vessels [6][7]. This fluid buildup creates the visible, puffy swelling. Interestingly, people who are traveling to or are newer residents of areas where loiasis is common often experience more severe allergic reactions and larger swellings than those who have lived in high-transmission areas their whole lives [8][9].

Where Do They Occur and What Do They Feel Like?

Calabar swellings can appear anywhere on the body where the worm travels. However, they most frequently occur on the limbs (arms and legs) and the face, particularly around the eyelids [3][10]. You might also experience a related symptom called subconjunctival migration, which is when the worm is visible as it briefly migrates across the white of the eye [10].

When a swelling develops, you may notice the following:

  • Erythema: The skin over the swelling may appear slightly red, puffy, and feel tight [2][11].
  • Pruritus: The swollen area is often intensely itchy due to the allergic nature of the immune reaction [12][13].
  • Arthralgia: If the swelling occurs near a joint, such as your wrist or knee, it can cause aching or joint discomfort when you try to move it [12][13].

How Long Do They Last and What Should You Do?

Because Calabar swellings are directly tied to the movement of the adult worm, they are known in medical literature as “fugitive” or transient swellings [14][2]. They are temporary and typically last for several days before the swelling naturally resolves on its own as the worm leaves that specific tissue area [5][1].

However, the disappearance of a single swelling does not mean the infection is gone. The underlying Loa loa parasite remains active in your body [5]. To cure the infection and stop the swellings from returning, you must see a doctor for formal diagnosis (often through specialized blood tests or eye exams) and to discuss prescription antiparasitic treatment [1][15]. While you wait for medical treatment to eliminate the parasite, you can discuss safe options for temporary symptom relief, such as over-the-counter antihistamines or cold compresses, with your healthcare provider.

Common questions in this guide

What causes a Calabar swelling?
Calabar swellings are caused by a localized allergic reaction to the adult Loa loa worm as it migrates through the tissue just beneath your skin. Your immune system reacts to the proteins the worm releases, causing temporary inflammation and fluid buildup.
How long do Calabar swellings last?
These swellings are temporary and typically last for a few days before resolving on their own. However, the swelling disappearing does not mean the parasite is gone, and new swellings can eventually appear in different locations.
Where do Calabar swellings usually appear?
They can appear anywhere on the body, but most commonly occur on the arms, legs, and face. They are especially frequent around the eyelids and near joints such as the wrists and knees.
How do you treat Calabar swellings?
While cold compresses and over-the-counter antihistamines can provide temporary relief from itching and discomfort, they do not cure the underlying infection. You will need prescription antiparasitic medication from a doctor to eliminate the Loa loa parasite.

Questions to Ask Your Doctor

Curated prompts to bring to your next appointment.

  1. 1.What antiparasitic medications are appropriate for my specific case, and what side effects should I watch for when treatment begins?
  2. 2.How can we confirm my diagnosis—will I need a specific blood test to check for microfilariae, or a detailed eye exam?
  3. 3.Are there safe over-the-counter options, such as antihistamines or cold compresses, that I can use to manage the intense itching and discomfort when a new swelling appears?
  4. 4.Given my travel history or residence in an endemic area, should I be tested for other co-infections before starting treatment?

Questions For You

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References

References (15)
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    Evaluation of a novel biplex rapid diagnostic test for antibody responses to Loa loa and Onchocerca volvulus infections.

    Campillo JT, Biamonte MA, Hemilembolo MC, et al.

    PLoS neglected tropical diseases 2024; (18(10)):e0012567 doi:10.1371/journal.pntd.0012567.

    PMID: 39388495
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    Loa loa filariasis in a tropical savanna area: report of one case in Ouagadougou.

    Ouédraogo NA, Korsaga-Somé N, Traoré F, et al.

    International journal of dermatology 2020; (59(4)):482-483 doi:10.1111/ijd.14782.

    PMID: 31975376
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    Clinical and epidemiological features of imported loiasis in Beijing: a report from patients returned from Africa.

    Li X, Huang M, Bi K, et al.

    BMC infectious diseases 2024; (24(1)):714 doi:10.1186/s12879-024-09620-6.

    PMID: 39033158
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    Mouse models of Loa loa.

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    PMID: 30926803
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    Atypical Clinical Manifestations of Loiasis and Their Relevance for Endemic Populations.

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    Open forum infectious diseases 2019; (6(11)):ofz417 doi:10.1093/ofid/ofz417.

    PMID: 31696139
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    Identification and characterization of Loa loa antigens responsible for cross-reactivity with rapid diagnostic tests for lymphatic filariasis.

    Hertz MI, Nana-Djeunga H, Kamgno J, et al.

    PLoS neglected tropical diseases 2018; (12(11)):e0006963 doi:10.1371/journal.pntd.0006963.

    PMID: 30444866
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    Disability and quality of life assessment using WHODAS-12 items 2.0 and EQ-5D-5L in a rural area endemic for loiasis in the Republic of Congo: A population-based cross-sectional study (the MorLo project).

    Hemilembolo MC, Campillo JT, Dupasquier V, et al.

    PLoS neglected tropical diseases 2025; (19(9)):e0013491 doi:10.1371/journal.pntd.0013491.

    PMID: 40953102
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    Imported loiasis in France: a retrospective analysis of 167 cases with comparison between sub-Saharan and non sub-Saharan African patients.

    Bouchaud O, Matheron S, Loarec A, et al.

    BMC infectious diseases 2020; (20(1)):63 doi:10.1186/s12879-019-4740-6.

    PMID: 31959110
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    Clinical Features of Imported Loiasis: A Case Series from the Hospital for Tropical Diseases, London.

    Saito M, Armstrong M, Boadi S, et al.

    The American journal of tropical medicine and hygiene 2015; (93(3)):607-11 doi:10.4269/ajtmh.15-0214.

    PMID: 26101271
  10. 10

    Ocular filariasis manifesting as an orbital cellulitis and conjunctival nodule: a case report.

    Albou J, Chotard G

    Orbit (Amsterdam, Netherlands) 2026; 1 doi:10.1080/01676830.2025.2609909.

    PMID: 41498296
  11. 11

    Dirofilariasis presenting with recurrent solitary erythematous swellings and creeping dermatitis.

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    Journal of travel medicine 2025; (32(8)) doi:10.1093/jtm/taaf100.

    PMID: 41036666
  12. 12

    [Case report: Two patients with eye worm and recurrent swelling of the extremities].

    Bragason DT, Gottfredsdottir MS, Johannsson B, Gottfredsson M

    Laeknabladid 2018; (104(9)):395-398 doi:10.17992/lbl.2018.09.197.

    PMID: 30178753
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    Incidence of loiasis clinical manifestations in a rural area of the Republic of Congo: Results from a longitudinal prospective study (the MorLo project).

    Campillo JT, Pakat-Pambou BM, Sahm B, et al.

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    Loiasis is endemic in the Ndikinimeki Health District (Centre Region, Cameroon) but does not represent a hindrance to onchocerciasis elimination.

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This page provides educational information about Calabar swellings and loiasis. It is not a substitute for professional medical advice. Always consult a healthcare provider, particularly an infectious disease specialist, for diagnosis and treatment of parasitic infections.

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