Why Do Mosquito Bites Itch?

Question: Why Do Mosquito Bites Itch?

Most people experience some kind of skin reaction after being bitten by a mosquito. The pain of the bite and the red bump that follows can be tolerated, but the persistent itching is enough to drive you crazy. Why do mosquito bites itch?

Answer:

Only the female mosquito feeds on blood. Though we commonly call them mosquito bites, she's not really biting you at all. The mosquito pierces the upper layer of your skin with her proboscis, a straw-like mouthpart that allows her to drink fluids. Once the proboscis breaks through the epidermis, the mosquito uses it to search for a blood vessel in the dermal layer underneath.

When she locates a vessel, the mosquito releases some of her saliva into the wound. Mosquito saliva contains an anti-coagulant that keeps your blood flowing until she is finished with her meal.

Now your immune system realizes something is going on, and histamine is produced to combat the foreign substance. The histamine reaches the area under attack, causing blood vessels there to swell. It's the action of the histamine that causes the red bump, called a wheal.

But what about the itching? When the blood vessels expand, nerves in the area become irritated by the swelling. You feel this irritation as an itchy sensation.