For the sake of brevity, I will focus on the microbiome and how it affects the scalp. The metabolic exchanges between the scalp surface and microbiome support the growth of microbial biofilms in a symbiotic, commensal or pathologic form.1 There is a hypothesis stating that collapse of a balanced microbiome, such as reduction in microbial diversity and overgrowth of some microbial species, may be linked with skin problems.2 As it relates to the scalp, seborrheic dermatitis (SD) is characterized by flaking, itching, burning and pain. It affects nearly half of the post-pubertal population regardless of ethnicity or gender.2 It has always been taught that fungi of the Malassezia spp are responsible for SD. A study involving 102 Korean volunteers revealed that although Staphylococcal spp and Malassezia restricta were associated with a higher incidence of scalp disease, it was bacteria that has a stronger relationship with the severity of dandruff compared to fungi.2 Researchers concluded that a bacterial/fungal disequilibrium, or collapse may be the main cause of seborrheic dermatitis.
In one study involving the scalps of 140 Indian women to determine species diversity and taxonomic composition of healthy and dandruff scalp, a significant enrichment of biosynthesis and metabolism pathways of vitamins and cofactors was observed in the bacterial microbiome of healthy scalp compared to the dandruff scalp.1 The biotin metabolism pathway was found to be significantly enriched in in the healthy scalp as compared to dandruff scalp.1 Biotin and amino acids are reported to play a beneficial role in maintaining healthy hair and scalp and controlling dandruff.1 Nicotinate and nicotinamide pathway involved in vitamin B3 (niacin) production maintains scalp health and increases hair diameter.1 Vitamins B6 and B12 are essential for supporting hair structures and the amino acid lysine is known to reduce hair loss.1 There is a possible beneficial role of bacterial scalp microbiome and in supplying essential vitamins and amino acids to the host, just as the gut bacteria does.
Now let’s take a look at the actual hair follicle. Hair follicles extend from the skin surface to the dermis or subcutaneous tissue with direct connection to the sebaceous gland.3 As a result, microbes may reside deeply in the follicle. These immune-privileged sites are found around the stem cell-bearing bulge and around the anagen (actively growing hair) bulb. A collapse in this immune-privileged status of the hair follicle results in alopecia.3 This is a result of inflammation and invasion of cytotoxic T cells during the growth phase (anagen), leading premature entry of the hair follicle into the catagen (intermediate step before resting phase), inevitably leading to telogen and exogen, causing hair loss.3 In non-scarring alopecias such as alopecia areata, the inflammation is peri-bulbar so stem cells are spared, re-entry into the regular hair cycle occurs and hair re-growth occurs after the inflammation resolves.3 If disruption affects the bulge area, where stem cells reside, the hair loss is scarring and therefore permanent, in cases such as lichen planopilaris, folliculitis decalvans, and perhaps, central centrifugal cicatricial alopecia (CCCA)—an epidemic among women of African origin, African-American, European and Caribbean included.
Alterations in the microbiota, or the term dysbiosis, are found to be closely related to systematic inflammations and the metabolic syndromes.4 So, what disrupts our microbiome, our normal flora, and how do we address it? The assault on the normal flora of the human body is multifactorial. The American diet is a major factor. Due to the aberrant diet habitats, which are among the many causative environmental factors that lead to the situation of intestinal dysbiosis, a compromised host ability to maintain a balanced gut is a challenge.4 The use of antibiotics is known to disrupt the normal flora of the gut, so when I prescribe an antibiotic, I ask my patients to take a probiotic, preferably not in dairy form as to avoid inflammation.
The term “probiotic” refers to live microorganisms that show beneficial effects on the health of the host.4 The current definition of a probiotic indicates specific bacterial strain(s) that can effectively promote the health of humans.4 Subsequently, the term “prebiotic” was generally accepted to selectively refer to food ingredients that are non-digestible and show beneficial effects on the host by stimulating the growth and/or activity of probiotics in the colon after fermentation.4 Synbiotics refer to food ingredients or dietary supplements composed of both probiotics and prebiotics in a form of synergism. The function of synbiotics can be either complementary or synergistic.4
The change of relative abundances between different bacterial phyla may result in development of chronic inflammation.4 Among these, the increased Proteobacteria number may enhance chronic and systemic inflammations, leading to increased permeability of the intestine (leaky gut) and systematic inflammations in host.4 What if you have leaky gut? If you suffer from chronic diarrhea, constipation, gas or bloating, brain fog, excess fatigue, joint pain, visit a gastroenterologist. The gut is their forté. They will try to tell you the intestines are the largest organ in the body, but everyone else knows that skin is the largest organ of the human body and it is also the organ that protects you from environmental assaults such as pollutants and free radicals.
The bottom line? Be good to your skin, hair, scalp, nails—and gut. Your overall health and life will be better for it.
- Saxena, Rituja et al. Comparison of Healthy and Dandruff Scalp Microbiome Reveals the Role of Commensals in Scalp Health. Frontiers in Cellular and Infection Microbiology. October 2018, Vol 8, Article 346.
- Kuo-Feng Huang et al. Collapse of human scalp microbiome network in dandruff and seborrheic dermatitis. Experimental Dermatology 2017, Letters to the Editor pp. 835-837.
- Polak-Witka, K., Rudnicka, L., Blume-Peytavi, U., and Vogt, Annika. The role of the microbiome in scalp hair follicle biology and disease. Experimental Dermatology. 2019;1-9.
- Tsai et al. Probiotics, prebiotics and amelioration of diseases. Journal of Biomedical Science. 2019; 26:3.
Sharleen St. Surin-Lord
Dr. Sharleen St. Surin-Lord is a board-certified dermatologist who has been practicing for more than 13 years. She is in private practice at Visage Dermatology, Largo MD. She also teaches at the University of Maryland Capital Regional Health System in Maryland and she is an assistant professor of dermatology at Howard University College of Medicine. “Dr. Sharleen” is a member of the American Hair Research Society and you can follow her on Twitter, Instagram, and Facebook as DermHairDoc.