Insect Bite Reactions: What an Insect Bite Allergy Looks Like

A mosquito, midge, or bee bite usually results in an itchy bump and resolves within a few days. Insect bites are usually not dangerous, but they can sometimes become infected or cause a serious allergic reaction. We explain what an insect bite allergy looks like and where a normal skin reaction ends.

Normal reaction to a bite vs. allergy: what's the difference

The main symptoms of a bite are pain at the site of the sting and slight swelling. The bump may be red; on dark skin, redness is less visible but can be felt, and a mark from the bite remains. Some bites occur in groups on a small area. With a mild allergic reaction, the skin around the bite itches and becomes raised. If an infection develops, the area becomes more swollen and painful, the skin is hot, and pus or fluid appears. A normal bite resolves within a few days.

• Normal reaction — pain and slight swelling at the bite site.
• Mild allergy — itching and raised skin around the bite.
• Infection — hot red skin, increasing pain, pus or fluid.
• A target-shaped rash after a tick bite — a sign of Lyme disease.

What flea, midge, and tick bites look like

Mosquitoes leave small raised itchy bumps. Midges leave similar small bites, but in groups. Flea bites are usually found below the knees, also in groups. Ticks are small arachnids that attach to the skin; a target-shaped rash is a symptom of Lyme disease after a tick bite. Horseflies bite deeply and painfully, drawing blood, and such sites often become infected. Scabies mites cause very itchy lumps, sometimes with small blisters.

Bee and wasp sting allergy

After a bee, wasp, or hornet sting, a small mark from the stinger remains, and sometimes the stinger itself becomes lodged in the skin. Bites from bees, wasps, hornets, and fire ants usually hurt, whereas mosquitoes and fleas mainly itch. People with a confirmed severe reaction to bites, up to and including anaphylaxis, carry an emergency kit with epinephrine.

Why insect allergy occurs

Allergy is a hypersensitivity that the adaptive immune system develops in response to normally harmless substances, allergens. The reaction occurs on repeated contact with the allergen in an already sensitized person, and sensitization itself does not necessarily result in allergy. In clinical guidelines, the term is more often applied to IgE-mediated reactions, which are type I according to the Gell and Coombs classification. Pseudoallergy also exists: reactions similar in presentation occur on the very first contact, without prior sensitization and without IgE. Allergic diseases are common: at least one of them affects 8–10% of people worldwide, and in some regions of Russia, 10–35% of the population.

Warning signs of a severe reaction

A bite is usually not dangerous and resolves on its own, but it can sometimes cause a serious allergic reaction or become infected. Ticks are a separate matter: a target-shaped rash indicates Lyme disease, and a doctor is needed here. If the bite is hot, red, painful, the swelling is increasing, or pus and fluid appear, seek medical attention.

A bite by itself is not a reason to call an ambulance. 103 or 112 are needed if a serious allergic reaction develops after a bite, up to and including anaphylaxis, especially in a person with a known severe allergy to insect bites.

How a doctor identifies a bite allergy

The doctor examines the bite site and asks questions, distinguishes allergy from infection and from rashes of other origin, and if insect allergy is suspected, refers the patient to an allergist. This material is for reference: it does not replace a doctor's consultation, and if in doubt, it is best to make a decision together with an allergist.

This content is for reference and does not replace a doctor's consultation. Medical disclaimer