十万个为什么·科学启蒙30篇（4）
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Why Mosquito Bites Cause Itchy Bumps
为什么蚊子叮咬会起包发痒
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When a mosquito bites, it injects saliva containing anticoagulants to keep your blood flowing.
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Your immune system recognizes these foreign proteins as threats and releases histamine in response.
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Histamine makes nearby blood vessels widen and become leakier, causing swelling and redness.
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It also stimulates nerve endings, which sends itch signals to your brain.
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The bump forms because fluid accumulates under the skin where the bite occurred.
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Scratching worsens irritation and may let bacteria enter, risking infection.
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Children often react more strongly than adults because their immune systems are still learning.
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Antihistamine creams reduce itching by blocking histamine’s effects on skin receptors.
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Some people develop little or no reaction after repeated exposure over many years.
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Scientists study mosquito saliva to design better repellents and allergy treatments.