Why do mosquito bites itch?
The itch isn’t from the bite itself, it’s your immune system reacting to the mosquito’s spit. When a mosquito feeds it injects saliva, your body releases histamine to fight it, and histamine makes the skin swell and the nerves itch.
Only females bite
Only female mosquitoes drink blood, they need the protein to make eggs. Her mouth is a bundle of fine needles that slides through the skin to find a tiny blood vessel.
Share this stepShe leaves her spit behind
While she drinks, she pumps saliva into the skin. It stops your blood from clotting so she can drink freely. Proteins in that saliva are what your body reacts to.
Share this stepYour immune cells sound the alarm
Immune cells in the skin spot the foreign proteins and release histamine. It makes small blood vessels leak a little fluid, which causes the red, swollen bump.
Share this stepHistamine sets off the itch nerves
Histamine also activates special nerve endings that send an itch signal to your brain. Scratching gives a moment of relief but releases more histamine, so the itch comes back stronger.
Share this stepThe itch is your own defense at work.
Salivahistamineitch
Cooling the bite, a mild hydrocortisone cream or an antihistamine tablet can calm it. Try not to scratch: broken skin can get infected. Most bites settle within a few days.
Common follow-up questions
Why do some people get bitten more?
Mosquitoes find you by the carbon dioxide you breathe out, body heat and skin odor. People who breathe out more or smell more attractive to them get bitten more. Blood type has weak evidence at best.
Why do some people react more than others?
Reactions depend on your immune system. Children and people new to a type of mosquito often swell more. Some people who are bitten a lot become less sensitive over time.
Does hot water stop the itch?
Some people use heated bite pens or a warm spoon, and small studies suggest it can help briefly. Be careful not to burn the skin, and avoid it on children.
When should a bite be checked by a doctor?
If the redness spreads, the bite becomes warm and painful with pus, or you get a fever. Seek help right away if you have trouble breathing or swelling of the face or throat.
