At a private club in downtown Manhattan, Ms. Sarandon, wearing skinny jeans, combat boots and a striped cotton top, sipped tea as her fluffy dog, a Pomeranian mix named Penny who has her own Twitter account, cuddled up by her feet.

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"In contrast to, say, dust mites, which are heavy and sink quickly to the ground, both cat and dog dander are light and fluffy allergens, and they stay afloat for hours, " says Dr. Miranowski.

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Who can resist those big puppy-dog eyes, floppy ears and fluffy tail?

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