Mosquito bites are the itchy bumps that appear after mosquitoes use their mouthparts to puncture your skin and feed on your blood. The bump usually clears up on its own in a few days. 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 bite signs include:
A puffy, white and reddish 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
Small blisters instead of hard bumps
Dark spots that look like bruises
More-severe reactions may be experienced by children, adults not previously exposed to the type of mosquito that bit them, and people with immune system disorders. In these people, mosquito bites sometimes trigger:

A large area of swelling and redness
Low-grade fever
Hives
Swollen lymph nodes

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.

Mosquitoes select their victims by evaluating scent, exhaled carbon dioxide and the chemicals in a person's

Eliminate standing water, which mosquitoes need to breed. To keep your house and yard free of mosquito pools:

Unclog roof gutters.
Empty children's wading pools at least once a week, and preferably more often.
Change water in birdbaths at least weekly.
Get rid of old tires in your yard.
Empty outdoor flower pots regularly or store them upside down so that they can't collect water.
Drain your fire pit if water collects there.

https://www.mayoclinic.org