A study of U.S. military data collected during the First and Second World Wars found that the introduction of salt iodization in the U.S. in the 1920s resulted in an increase in IQ, by approximately one standard deviation, for the quarter of the U.S. population most deficient in iodine, explaining about "one decades worth of the upward trend in IQ" in the U.S. (i.e., the Flynn effect). The same study documented "a large increase in thyroid-related deaths following the countrywide adoption of iodized salt, which affected mostly older individuals in localities with high prevalence of iodine deficiency".In iodine-deficient or mildly iodine-deficient areas of Europe, iodine deficiency is frequent during pregnancy despite the widespread use of iodised salt, posing risks to the neurodevelopment of foetuses. In one study performed in a mildly iodine-deficient area, iodine deficiency was found to be present in more than half of breastfeeding women; in contrast, the majority of their newborns had iodine excess, mostly due to neonatal exposure to iodine-containing disinfectants. A 2014 meta-analysis found that iodine supplementation "improves some maternal thyroid indices and may benefit aspects of cognitive function in school-age children, even in marginally iodine-deficient areas".
The term acne cosmetica refers to acne caused by or aggravated by cosmetics. : 240   The mechanism is thought to be chemically induced plugging of the pilosebaceous orifice. This became a significant problem for dermatologists in the 1970s and 1980s, but with the improved formulations produced by cosmetic chemists in the decades since, a diagnosis of acne cosmetica has become relatively rare in dermatological practice. The terms "non-comedogenic" and "non-acne(i)genic" appeared on moisturizers and other cosmetic compounds as manufacturers introduced re-formulations—sometimes associated with claims that the products were "oil-free" or "water-based". Although early work produced lists of comedogenic chemicals in various strengths and vehicles, it became apparent that one could not predict the actual comedogenicity of a product from its contents; rather, the finished product itself needed use-testing.The production of a low-grade folliculitis by some components of cosmetic products has led to misdiagnosis on occasion. People may not attribute skin reactions to their cosmetics at first, but may notice worsening symptoms after using certain face makeup, sunblock or lip products. Reactions are more likely to occur if applied cosmetics are left on and not stripped after wearing them. See also
List of cutaneous conditions

References


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