There has long been known to be a link between stress and the immune system. Allergies occur when the immune system goes into overdrive and a study of 28 people by researchers at Ohio State University looked into the links between stress and allergies. The participants' anxiety levels were measured at the start of the study using a standardised questionnaire and they underwent pinprick tests to measure their reactions to allergens. The participants were also placed under stress by being asked to deliver a ten-minute talk and do maths questions without using a pen and paper (the stress condition). The researchers then measured the size of the weals on the participants' arms before and after they experienced the stress condition. Participants who had only moderate levels of 'background' anxiety had weals 75% larger after the stress experiment but for people who were already highly anxious at the start of the study their weals were more than twice as large after the stress test. Anxious people were four times more likely to have a stronger reaction to the skin test one day later after the stressful condition.
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