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by HowStuffWorks
The body's first line of defense against potentially dangerous invaders includes the mouth, eyes, lungs, stomach and nose. When your immune system reacts to an allergen, these body parts can potentially become battlegrounds.
Signs of the raging battle can include one or more of these conditions: sneezing; watery, swollen, or red eyes; nasal congestion; sinus inflammation and pressure; runny nose;...
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