Worms are often unnoticed as they travel through subcutaneous tissues but can be painful as pass over the eyeball or bridge of the nose. Swelling of the conjunctiva and eye lid sometimes accompanies the worm's presence. Patients may describe literally seeing something crawl across their eye.
Calabar swellings (see picture below), or local edema of the subcutaneous tissue, are caused by an allergic reaction to dead worms or the metabolic products of the worms. The swellings are typically several inches in diameter and subside after a few days to a few weeks. They can be tender and painful. Calabar swellings can occur anywhere on the body but are often found on the forearms and wrists.
Complications may arise if worms lodge in unusual sites. Scrotal swelling, bowel obstruction, inflammation of renal glomeruli, endocarditis, retinopathy, arthritis, and peripheral neuropathy have all been seen in persons infected with Loa loa.
As is true with many parasites, Loa loa often increases the numbers of eosinophils, the immune cell that fights parasitic infections, in the blood.
Loa loa does not cause serious long term damage to humans.
