Cold Shock for Hair Growth
How cryotherapy wakes dormant hair follicles
Summary
Although dermatologists will sometimes blame elevated testosterone for male baldness, that's a popular misconception.
Men lose hair for a number of reasons that could include:
thyroid disorders,
poor blood flow to the scalp,
inflammation and other autoimmune disorders,
light starvation.
Cold shock can help resolve all of these. Juan Ricardo Perez-Escamilla says he started regrowing his own hair after adopting a regular practice of cold showers.
Can Cold Grow Hair?
I recently interviewed a Mexican man who claims that cold showers are regrowing hair on his bald head. His name is Juan Ricardo Perez Escamilla Gonzalez and he first came to my attention because the author and breathwork specialist James Nestor was talking about him in a reel on Instagram.
Juan says he went completely bald in his 30's and he blames hot showers for his hair loss. When you listen to the podcast, you'll see that I'm skeptical of that explanation. I think it's more likely that he suffered from a thyroid disorder that a regular practice of cold therapy corrected.
As I wrote in Resolving Raynaud's, a consistent practice of cold therapy will cause the body to recruit new brown fat to both defend core body temperature via cold thermogenesis and convert inactive thyroid hormone into the active form. Moreover, brown fat (brown adipose tissue, BAT) modulates thyroid function. The brown fat and thyroid are in constant communication with one another, both regulating the activity of the other. That's how ice baths help resolve Hashimoto's.
Hair loss is typical for people suffering from thyroid dysfunction, so I theorized that Juan's regular cold showers had recruited brown fat, corrected his thyroid disorder, and allowed his hair to regrow.
What neither Juan nor I knew at the time of our podcast is that cryotherapy has been used in clinical practice to treat patchy baldness since at least the mid-1980's. That's when Chinese scientists first reported the results obtained by treating 123 bald men with liquid nitrogen therapy (Lei et al. 1991).
The Lifecycle of the Hair Follicle
Hair follicles cycle through anagen (growth), catagen (regression), and telogen (rest). The anagen phase is triggered by activity in stem cells that reside at the base of the follicle. There, cells called keratocytes produce new keratin, the primary protein from which hair is constructed. The activity in these cells can be metabolically expensive, so hair must receive adequate blood flow to deliver the necessary nutrients.
One of the most common misconceptions about hair growth is that baldness is caused by high levels of circulating testosterone. In theory, high testosterone results in high levels of dihydrotestosterone (DHT), which is derived from testosterone and will signal hair follicles to shut down. Logically, it would make sense if high levels of DHT in the bloodstream were reaching hair follicles, then that DHT would terminate the anagen phase and initiate a premature telogen phase from which the hair follicle would never emerge.
But that's not what happens.
Hair follicles do not absorb DHT from the bloodstream. They synthesize it themselves.
DHT is not the cause of baldness. It is the mechanism.
Reawakening Dormant Hair Follicles
More than a dozen studies support Juan's thesis that cold will awaken hair follicles stuck in the telogen phase and return them to the anagen, or growth phase (Lim & Lee 2023). Most studies use rapid cooling, or cold shock, with liquid nitrogen or liquid carbon dioxide.
When thermoreceptors sense the sudden, frigid temperatures, they signal the hypothalamus in the brain and activate the sympathetic division of the central nervous system, causing smooth muscle tissue to contract and brown fat to begin cold thermogenesis. There are two types of smooth muscle tissue. The first surrounds blood vessels and causes vasoconstriction to shut down bloodflow to cold areas of skin, minimizing heat loss. The second is called the arrector pili and those muscles are attached to the hair follicles to give you goosebumps.
When you’re cold or startled, sympathetic nerves release norepinephrine, contract the arrector pili, cause hair to stand up, and make skin dimples around the shaft of the hair follicle in a process called piloerection. You might notice this in cats or dogs when their fur seems to swell, making them look bigger when they feel threatened. Although humans don't have fur, we do have the same nervous system response for exercising the hair follicle (Shwartz et al. 2020).
When the cold subsides and the skin rewarms, the blood vessels must dilate to restore circulation. Over time (about two weeks) a regular practice of deliberate cold exposure will cause the body to remodel the microscopic blood vessels that supply the scalp with nutrients necessary for hair growth (Jun & Lee 2017, Abdel-Majid et al. 2018). By increasing concentration of a signaling molecule called VEGF, cold stimulates a process called angiogenesis (synthesis of new blood vessels), improving the supply of nutrients to the skin (Sugasawa et al. 2016).
Additional benefits of cold might include a reduction of inflammation and other autoimmune responses that could interfere with hair follicle function (Radmanesh & Azar-Beig 2013) and activation of stem cell activity in the base of the follicle. When cooled fast, no more than 10F, researchers found that cold is associated with increased levels of Cold Induced Reactive Protein (CIRP) and Binding Molecule 3 (RBM3) that suggest increased stem cell activity in the follicle (Lee et al. 2024 [mice]). However, too much cold reversed the effect, shutting activity in the follicles down.
Hair Growth Protocols for Cold Plunge
Until my podcast with Juan, it had never occured to me that there might be protocols by which an ice bath might stimulate the scalp for increasing hair growth. Having reviewed the research, it does seem like we could propose some tentative guidelines:
Do a Quick Head Dunk in Your Ice Bath. The scalp must be cooled quickly to induce production of cold shock proteins like CIRP and RMB3, stimulate some vasoconstriction, and cause angiogenesis -- but don't stay under very long. My preference is to dunk my head at the beginning of my ice bath. Others prefer to finish with a head dunk. The principal difference between the two is in the timing of sympathetic activation. When you head dunk at the beginning, all the sympathetic activation is at the start of your plunge. If you wait until the end, wetting your dry head with cold water will restart the process of sympathetic activation (gasp reflex) and require a new transition to the parasympathetic that I call pendulation.
Olivia Pompa DC demonstrates the pendulation protocol that Andrew Sheridan designed. Going in a little bit at a time ensures cycling between activation of sympathetic and parasympathetic. Get Sunlight with UV and Forest Light with Green on Your Scalp. It should come as no suprise that the human scalp is sensitive to the light environment. In Hair Thrives Under Forest Light I described the importance of exposing the scalp to 532nm green and 730nm red/near infrared (NIR) light to energize melanin at depth below the surface of the skin that matches the base of the hair follicle. This combination of green and red/NIR is called forest light because it matches the light environment of the shady forest and it is essential for healthy hair. However, to ensure that the scalp has enough melanin for the forest light to energize, the scalp must also be exposed to ultraviolet (UV) light in sunshine. This UV light does not penetrate to the depth of the hair follicle, but it cause melanocyte activity to produce more melanin. Violet light at 380 nm is particularly effective for melanogenesis, without the damaging effects of UVB. If you're already getting enough UV, then you can get forest light from the MyGreen Hair Hood. If you're not getting enough UV, then you'll need the MyGreen Basking Lamp to ensure you do it safely.
References
Abdel-Majid EM, Abdel-Kader DS, Allam AA. Liquid nitrogen cryotherapy in the treatment of alopecia areata. Journal of Current Medical Research and Practice. 2018 Sep 1;3(3):187-90.
Jun M, Lee WS. Therapeutic effect of superficial cryotherapy on alopecia areata: a prospective, split-scalp study in patients with multiple alopecia patches. Annals of Dermatology. 2017 Dec 1;29(6):722-7.
Lee S, Ohn J, Kang BM, Hwang ST, Kwon O. Activation of mitochondrial aldehyde dehydrogenase 2 promotes hair growth in human hair follicles. Journal of Advanced Research. 2024 Oct 1;64:237-47.
Lei Y, Nie Y, Zhang JM, Liao DY, Li H, Man MQ. Effect of superficial hypothermic cryotherapy with liquid nitrogen on alopecia areata. Arch Dermatol. 1991;127(12):1851-2.
Lim SH, Lee WS. Hair regrowth outcomes of superficial cryotherapy in patients with alopecia areata: a systematic review. Ann Dermatol. 2023;35(6):464-467.
Radmanesh M, Azar-Beig M. Cryotherapy as an alternative therapy for the treatment of recalcitrant alopecia areata. Iran J Dermatol. 2013;16:49-52.
Shwartz Y, Gonzalez-Celeiro M, Chen CL, Pasolli HA, Sheu SH, Fan SM, Shamsi F, Assaad S, Lin ET, Zhang B, Tsai PC, He M, Tseng YH, Lin SJ, Hsu YC. Cell types promoting goosebumps form a niche to regulate hair follicle stem cells. Cell. 2020 Aug 6;182(3):578-593.e19. doi: 10.1016/j.cell.2020.06.031.
Sugasawa T, Mukai N, Tamura K, Tamba T, Mori S, Miyashiro Y, et al. Effects of cold stimulation on mitochondrial activity and VEGF expression in vitro. Int J Sports Med. 2016 Sep;37(10):766-78. doi: 10.1055/s-0042-102659.
About the Author
Thomas P Seager, PhD is an Associate Professor in the School of Sustainable Engineering at Arizona State University. Seager co-founded the Morozko Forge ice bath company and is an expert in the use of ice baths for0building metabolic and psychological resilience.
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