Boosting certain cell signals can prevent hair loss from chemotherapy and radiation.
Chemical treatments weaken hair's thermal stability and structure.
May 2016 in “Portuguese National Funding Agency for Science, Research and Technology (RCAAP Project by FCT)” 
7 citations
,
January 2015 in “Hair therapy & transplantation” Air pollution can cause hair loss, and using antioxidants, special shampoos, and coconut oil can improve scalp health and hair density.
32 citations
,
January 2018 in “American Journal of Clinical Dermatology” Hormone therapy affects hair growth in transgender individuals, with testosterone potentially causing hair loss in trans men and estrogen reducing facial/body hair in trans women; treatment options vary.
January 2020 in “Estetologia Medyczna i Kosmetologia” Most ingredients in anti-hair loss products lack scientific proof of effectiveness.
Some factors can either promote or inhibit hair growth.
2 citations
,
January 2013 in “Advances in Experimental Medicine and Biology” Taurine might help prevent hair loss caused by stress.
31 citations
,
January 1993 in “Skin Pharmacology and Physiology” Potassium channel openers can boost hair growth by stimulating DNA in hair follicles.
January 2020 in “Journal of dermatology research and therapy” Most over-the-counter hair loss treatments lack strong evidence of effectiveness but cost nearly as much as the proven treatment, minoxidil.