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    GlossaryAllergic Reactions

    immune system overreacts to harmless substances, causing symptoms

    An allergic reaction, also known as a hypersensitivity reaction, occurs when the immune system mistakenly identifies a harmless substance (allergen) as a threat and overreacts to it. This can lead to symptoms ranging from mild, such as itching and sneezing, to severe, such as anaphylaxis, which can be life-threatening. Common allergens include pollen, pet dander, certain foods, and insect stings.

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