A swollen bite on the leg: what to watch for

The skin may become itchy, raised and pink because the immune system reacts to material left by an insect. Swelling can look prominent around the ankle because fluid collects in the lower leg, particularly after standing.

A reaction centred on the bite that is mainly itchy fits local inflammation. Infection is more concerning when tenderness, heat and redness steadily increase, pus appears, or the red area extends away from the bite. Swelling of the entire leg can also have causes unrelated to the bite and deserves medical review.

Sudden deeper swelling can occur with angioedema, especially when the lips, tongue, face or throat are also affected. The urgency comes from airway symptoms, not from the size of the skin mark.

Wash the site gently, remove a visible stinger by scraping it sideways, and place a cool wrapped compress over the skin. Rest with the leg raised and avoid tight footwear or scratching. A pharmacist can advise whether an oral antihistamine or soothing skin treatment suits your age, health and medicines.

Check the bite periodically. Note whether the swelling is settling, remaining local or moving beyond the original area. Do not puncture a blister or press on a firm centre, since damaged skin is more vulnerable to infection.

Call emergency services if swelling involves the tongue or throat, breathing becomes difficult, the voice changes, or there is faintness or collapse. These can be signs of a severe allergic reaction.

Seek prompt assessment when swelling is rapidly increasing, the whole calf or leg becomes swollen, walking is difficult, pain is severe, or the skin is hot with expanding redness. Fever, red streaks, drainage, numbness or dark discoloration also require timely care.

Describe when the swelling began, how quickly it changed and whether there is itching, pain, warmth, fever or breathlessness. Ask whether the appearance suggests allergy, infection or another cause of one-sided leg swelling, and whether your current medicines or previous severe reactions change the care plan.