TLDR External factors can significantly affect hair cortisol levels, so it's not always a reliable stress marker.
The study investigated the impact of external factors on hair cortisol concentrations in sheep, highlighting the potential for local cortisol production in the skin to affect these measurements. Eight sheep were subjected to various treatments, including extensive brushing and the application of a synthetic glucocorticoid, over three weeks. Results showed that hair cortisol concentrations significantly increased in areas treated with brushing or glucocorticoid, while no significant changes were observed with other treatments. The study concluded that caution should be exercised when using hair cortisol as a marker for chronic stress, as external factors can significantly influence the results.
118 citations
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October 2014 in “Journal of Dairy Science” Tail switch hair is best for measuring cortisol in Holstein cows, with white hair and multiparous cows showing higher levels.
22 citations
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January 2010 in “Clinical Medicine Insights Endocrinology and Diabetes” Forearm hair has more cortisol than lower leg hair.
217 citations
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July 2009 in “Experimental and Clinical Endocrinology & Diabetes” Hair analysis can track past cortisol levels in Cushing's Syndrome patients.
489 citations
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June 2005 in “The FASEB Journal” Human hair follicles can produce cortisol like the body's stress response system.
11 citations
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June 2005 in “Veterinary Dermatology” Canine hair follicle cells convert progesterone into various metabolites, mainly cortisol.
May 2023 in “Animal Reproduction Update” High levels of cortisol in hair show long-term stress which can lower fertility in animals.
44 citations
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November 2018 in “Journal of applied ecology” Hair analysis for stress and reproductive hormones in wildlife needs more research for accuracy across species.
47 citations
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September 2016 in “Reviews in endocrine and metabolic disorders” The skin's ability to produce hormones is linked to various skin conditions, and better understanding this process could lead to new treatments.
8 citations
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October 2020 in “Infant behavior & development” Collecting hair for cortisol analysis is possible in low-income mother-toddler pairs.
11 citations
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April 2020 in “Animals” Moving horses to new places can increase their stress levels, as shown by higher stress hormone in their hair.
50 citations
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July 2018 in “Psychoneuroendocrinology” Hair cortisol can indicate long-term stress levels, but hair growth rate differences may affect accuracy.
