Mosquito bites are the itchy bumps that appear after mosquitos use their mouthparts to puncture your skin and feed on your blood. Most mosquito bites are harmless, but occasionally a mosquito bite causes a large area of swelling, soreness and redness. This type of reaction, most common in children, is sometimes referred to as skeeter syndrome.
Bites from mosquitoes carrying certain viruses or parasites can cause severe illness. Infected mosquitoes in many parts of the world transmit West Nile virus to humans. Other mosquito-borne infections include yellow fever, malaria and some types of brain infection (encephalitis).
Mosquito bites are caused by female mosquitoes feeding on your blood. Female mosquitoes have a mouthpart made to pierce skin and siphon off blood. Males lack this blood-sucking ability because they don’t produce eggs and so have no need for protein in blood.
As a biting mosquito fills itself with blood, it injects saliva into your skin. Proteins in the saliva trigger a mild immune system reaction that results in the characteristic itching and bump.
Most people never notice their first mosquito bites. After being bitten several times, though, you’re likely to start noticing, often almost immediately after the mosquito feeds. The signs include:
- A puffy, white bump that appears a few minutes after the bite
- A hard, itchy, reddish-brown bump, or multiple bumps, appearing a day or so after the bite or bites
- Swelling around bites
- Small blisters instead of hard bumps
- Dark spots that look like bruises
In children and people with immune system disorders, mosquito bites sometimes trigger:
- A large area of swelling and redness
- Low-grade fever
- Swollen lymph nodes
When to see a doctor
If mosquito bites seem to be associated with more-serious signs and symptoms — such as fever, headache and body aches — contact your doctor.