十万个为什么·科学启蒙30篇（4）

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为什么蚊子叮咬会起包发痒

When a mosquito bites, it injects saliva containing anticoagulants to keep your blood flowing.
Your immune system recognizes these foreign proteins as threats and releases histamine in response.
Histamine makes nearby blood vessels widen and become leakier, causing swelling and redness.
It also stimulates nerve endings, which sends itch signals to your brain.
The bump forms because fluid accumulates under the skin where the bite occurred.
Scratching worsens irritation and may let bacteria enter, risking infection.
Children often react more strongly than adults because their immune systems are still learning.
Antihistamine creams reduce itching by blocking histamine’s effects on skin receptors.
Some people develop little or no reaction after repeated exposure over many years.
Scientists study mosquito saliva to design better repellents and allergy treatments.