We typically think of skin only as it relates to beauty — but it’s actually really important to our overall health, too. After all, it’s the largest organ in the body, and the major interface between us and pretty much everything outside of us. Our skin is also home to a vast array of microbes and research is just now beginning to piece together the important role they play in our health.

The skin microbiome is different all over our bodies. These “bugs” will vary depending on the amount of light and whether the area is moist, dry, hairy, or oily and will change with age and gender. For instance, a hormonal, sweaty teenage boy will have a completely different microbiome to say a more sedentary, postmenopausal woman.

It is estimated that the average human has 1 trillion bacteria inhabiting their epidermis and hair follicles at any given moment. Skin microflora is typically non-pathogenic. In healthy dermal environments these bacteria are considered not harmful, or offer specific benefits including the prevention of transient pathogenic organisms from colonizing the skin surface.

pH matters

The epidermis is naturally acidic (pH 4-4.5) as a result of lactic acid produced in sweat by skin microorganisms. In mildly acidic skin environments, mutualistic flora (microorganisms that produce a mutual benefit for host and bacteria) such as Staphylococci, Micrococci, Corynebacterium and Propionibacteria flourish. However, transient bacteria such as Escherichia, Pseudomonas, Staphylococcus aureus or Candida albicans will not grow or thrive. Antimicrobial substances secreted by the skin are enhanced in acidic conditions and thus, stop the growth of harmful bacteria. Research has shown when skin is in an alkaline state bacteria detach from the skin and are more easily discarded from the dermis

In vitro, Propionibacterium acnes (P. acnes) have been found to flourish at pH values between 6 and 6.5, whereas its growth is considerably decreased at pH values less than 5.5. Researchers conducted a randomized, open, comparative three month trial assessing the use of acidic, or conventional soap in the prevention of acne lesions in acne-prone patients. Participants were asked to apply an acidic soap (syndets) or an alkaline/conventional soap to facial skin for 1 minute in the morning and in the evening. This study evaluated 120 adolescents and young adults who had been diagnosed with inflammatory acne lesions. The participant’s inflammatory acne lesions, itching, redness, and scaling were evaluated and analyzed. The alkaline/conventional soap participant group had an increase in inflammatory lesions, while the group using the acidic soap found their inflammatory acne lesions to decrease to statistically significant levels. The alkaline/conventional soap participant group reported a 40.4% increase in symptoms of irritation whereas the mildly acidic soap group experienced only 1.8% in symptoms of irritation. The researchers stated that the number of inflammatory acne lesions is clearly lower when an acidic soap is regularly used for cleansing the face as compared to an alkaline/conventional soap. This also proved to be the case with other types of topical skincare products.

Microbes involved in the formation of acne

  • – Staphylococcus aureous (bacterium)
  • – Propionibacterium acnes (bacterium)
  • – Demodex folliculorum (mite)
  • – Pityrosporum ovale (fungus)

A research article dated 2013 by Professors from Scholars Journal of Applied Medicine Sciences discovered that the most frequent bacteria isolated from acne patients were Staphylococcus aureus, which suggests it is possible that acne vulgaris is mainly caused by Staphylococcus aureus rather than Propionibacterium acnes.

  • Propionibacterium acnes (P. acnes) have been found to flourish at pH values between 6 and 6.5, whereas its growth is considerably decreased at pH values less than 5.5.
  • The optimal pH at which the growth of Staphylococcus aureus takes place is 7.0-7.5 (maximum is 9.3). However, growth was inhibited in the presence of 0.1% acetic acid (pH 5.1) (2)
  • Pityrosporum ovale, also known as Malassezia furfur, grows well in the pH range 7.5 – 8.3

Treatments that show great promise

For over a century, the connection existing between skin surface pH and microflora has been extensively investigated throughout published literature. Naturally designed as a protective barrier from environmental stressors, the skin is a complex organ that, under mildly acidic conditions, is able to maintain proper homeostasis and microflora which promote dermal longevity. Externally and internally, a variety of elements can inhibit the skin’s ability to maintain proper pH such as the natural aging process, genetics, ultraviolet radiation, hormones, oxidative stress, diet and tobacco use; thus rendering the skin susceptible to inflammatory disease such as acne and accelerated aging.

As researchers learn more about the microbes that keep us healthy, we are coming to understand how subtle imbalances in our microbial populations can also cause disease and how restoring this balance may lead to cures and while there is less research in the area of toxins and the skin microbiome specifically, we can infer that parabens, phthalates, sulfates, benzyl peroxide and others disrupt our skin’s delicate eco-environment highlighting the need to educate Doctors and patients on the favorable use of mildly acidic formulas and topical prebiotics/probiotics when treating these skin conditions.


  • (1) Korting HC, Braun-Falco O. The effect of detergents on skin pH and its consequences. Clin Dermatol 1996; 14: 23–27.
  • (2) http://www.rectofossal.com/bugs/staphylococcus-aureus/
  • (3) Peyton E. Weary, MD. Pityrosporum Ovale, Observations on Some Aspects of Host-Parasite Interrelationship. Arch Dermatol. 1968;98
  • (4):408-422. doi:10.1001/archderm.1968.01610160082018.
  • (4) Ts. Sarangua, A. Gurbadam, Ya. Enkhtur. Correlation Demodex Folliculorum and Skin Biophysical Parameters
  • (5) Saba M. A, Yosipovitch G. Skin pH: From Basic Science to Basic Skin Care. Acta Derm Venereol 2013; 93: 261–267.