What Do Calabar Swellings Look Like in Loiasis?

If you have spent time in West or Central Africa and are experiencing large, intensely itchy welts on your arms that vanish after a few days, these are very likely Calabar swellings. Also known as “fugitive swellings,” they are one of the most common and classic hallmark symptoms of loiasis (African eye worm) ^[1]. They can be confusing and alarming, but understanding what they look like and why they happen can help you differentiate them from normal bug bites or hives.

What They Look Like and Where They Appear

Calabar swellings appear as localized, red, raised areas of swelling just beneath the skin ^[2]. Medical professionals often refer to this as angioedema (swelling in the deep layers of the skin) ^[3].

• Appearance: Unlike swelling caused by fluid retention (like a swollen ankle from standing too long), Calabar swellings are typically non-pitting ^[2]. This means if you press firmly on the welt with your finger, it will feel firm or elastic and will not leave an indentation ^[2][1].
• Location: While they can appear anywhere on the body, they most frequently erupt on the extremities, particularly the wrists, forearms, ankles, and upper arms ^[4][5].
• Sensation: They are intensely itchy (pruritus) and can sometimes feel warm, tight, or be accompanied by aching in the nearby joints (arthralgia) ^[6][1].

How They Differ From Hives

It is easy to confuse a Calabar swelling with severe hives or a bad bug bite, but there are key differences:

• Duration and Movement: Standard hives often change shape, move around the body, or fade within a matter of hours. A Calabar swelling typically stays in one exact spot and lasts for a few days before disappearing ^[7][3].
• Depth: Bug bites are usually raised bumps on the very surface of the skin, whereas a Calabar swelling feels deeper and wider, involving the tissue underneath the skin ^[2].

Why They Happen

A common misconception is that the swelling is the actual Loa loa worm coiled up under your skin. This is not the case ^[8].

The swelling is actually an allergic and inflammatory reaction triggered by your immune system ^[8]. As the adult nematode (worm) migrates through your subcutaneous tissues (the layer just under your skin), it leaves behind proteins and waste ^[9][10]. Your body’s immune system recognizes these foreign substances and mounts a hypersensitive attack against them, resulting in the sudden, localized swelling ^[8][9].

Next Steps and Managing Symptoms

Because the adult worm is constantly on the move, a single welt will typically last for a few days before gradually vanishing on its own ^[7][3]. Once the swelling fades, the skin returns to normal.

However, because the underlying infection remains, the swellings are highly recurrent and will sporadically appear in different locations over time as the worm continues its migration ^[1][7]. Because intense scratching can sometimes lead to secondary skin infections, it is important to consult a healthcare provider or a tropical medicine specialist to discuss safe ways to soothe the itch ^[1].

The good news is that loiasis is completely treatable ^[11]. Be sure to explicitly mention your travel history to West or Central Africa, as this is the most critical clue your doctor needs to begin proper diagnostic testing and antiparasitic treatment ^[1].