Closing loopholes in background checks for gun purchases would reduce the risk of death and injury, doctors' and attorneys' groups say. Alexa Miller/Getty Images hide caption

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An overgrowth of Clostridium difficile bacteria can inflame the colon with a life-threatening infection. Dr. David Phillips/Getty Images/Visuals Unlimited hide caption

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In a landmark new study, researchers found that babies who consumed the equivalent of about 4 heaping teaspoons of peanut butter each week, starting when they were between 4 and 11 months old, were about 80 percent less likely to develop a peanut allergy by age 5. To avoid a choking hazard, doctors say kids should be fed peanuts mixed in other foods, not peanuts or globs of peanut butter. Anna/Flickr hide caption

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Most parents have a favorite child, psychologists say, even if they try to be fair. Hero Images Inc./Corbis hide caption

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There's a second chance coming for some people who didn't buy health insurance and would face a big tax penalty for 2015 otherwise. Laughing Stock/Corbis hide caption

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One form of carbapenem-resistant bacteria seen in culture. CRE bacteria are blamed for 600 deaths a year in the U.S. and can withstand treatment by virtually every kind of antibiotic. CDC hide caption

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