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Why Mosquito Bites Cause Itchy Bumps
为什么蚊子叮咬会起包发痒
精读先不看文字，完整听一遍。
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When a mosquito bites, it injects saliva containing anticoagulants to keep your blood flowing.蚊子叮咬时会注入含抗凝剂的唾液，防止血液凝固。
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Your immune system recognizes these foreign proteins as threats and releases histamine in response.你的免疫系统将这些外来蛋白识别为威胁，并释放组胺应对。
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Histamine makes nearby blood vessels widen and become leakier, causing swelling and redness.组胺使附近血管扩张、通透性增加，导致红肿。
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It also stimulates nerve endings, which sends itch signals to your brain.它还会刺激神经末梢，向大脑传递瘙痒信号。
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The bump forms because fluid accumulates under the skin where the bite occurred.叮咬处皮下积液，形成凸起的包块。
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Scratching worsens irritation and may let bacteria enter, risking infection.抓挠会加剧刺激，还可能让细菌侵入，引发感染。
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Children often react more strongly than adults because their immune systems are still learning.儿童免疫系统尚在发育，反应常比成人更强烈。
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Antihistamine creams reduce itching by blocking histamine’s effects on skin receptors.抗组胺药膏通过阻断组胺对皮肤受体的作用来止痒。
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Some people develop little or no reaction after repeated exposure over many years.部分人经多年反复接触后，反应微弱甚至消失。
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Scientists study mosquito saliva to design better repellents and allergy treatments.科学家研究蚊子唾液，以研发更有效的驱蚊剂和过敏疗法。
精读 · 大约 10 分钟
听 → 读 → 学表达 → 懂 → 今天会说这一句 → 跟读录音 → 自己说一句。
③ 学 · 重点表达
- Scratching worsens irritation and may let bacteria enter, risking infection. 抓挠会加剧刺激，还可能让细菌侵入，引发感染。
- Antihistamine creams reduce itching by blocking histamine’s effects on skin receptors. 抗组胺药膏通过阻断组胺对皮肤受体的作用来止痒。
- Scientists study mosquito saliva to design better repellents and allergy treatments. 科学家研究蚊子唾液，以研发更有效的驱蚊剂和过敏疗法。
④ 懂 · 选一选
⑤ 今天会说这一句
Scratching worsens irritation and may let bacteria enter, risking infection.
⑥ 跟读并录音
Scratching worsens irritation and may let bacteria enter, risking infection.
第一版：录下来、回听、再听标准音。系统打分以后再加。
⑦ 说 · 自己来一句
用今天的表达，自己说一句。
例子：Scratching worsens irritation and may let bacteria enter, risking infection.
已记下。连续天数以后会显示在课表里。
陈老师指导
课程开发中，敬请期待。成人和孩子都可以先自学听读、精读。
这边的讲解音轨还在做。想先跟着老师走完固定 30 课，可以去陈老师带读社（和自学通行不是同一份会员）。
课程开发中，敬请期待。