How hygiene products affect ocular surface and lids

It’s sort of funny-one of my childhood recollections is a discussion with my mother (the PhD in organic chemistry) regarding the virtues of Phisohex (hexaclorrphene, Septisol), a facial cleaner. “Phisohex is pH balanced,” she said, “so it is better for your skin.” At the time, the pH comment wasn’t important to me. What was important was that my mother said I should use it, and therefore the characteristic 1970s green bottle of Phisohex was standard at each sink in our home. Phisohex face cleaner has long since been removed for the over-the-counter (OTC) market in the U.S.; however an offshoot OTC product, pHisoderm is available. In fact, in Canada, pHisoderm products are marketed with skin pH raising and lowering properties (pHisoderm pH down for dry skin/pHisoderm pH up for oily skin.)

Maintaining pH balance

A quick review: pH (potential of hydrogen) is a measurement of the degree of the acidity or alkalinity of a solution as measured on a scale (pH scale) of 0 to 14. The midpoint of 7.0 on the pH scale represents a neutral solution-it is neither acid nor alkaline (i.e., water). Numbers below 7.0 indicate acidity; numbers greater than 7.0 indicate alkalinity. Typically, healthy skin has a slight acidic pH average of 5.5. Although controversial, many dermatologists believe that maintaining the skin surface physiological pH prevents overgrowth of microorganisms and protects the skin’s integrity and multifold functions.¹

The acid mantle is a thin, oily, protective film made up of sweat and sebum that sits on top of the outmost layer of our skin. Many of the contaminants that contact our skin, such as chemicals from the atmosphere and harmful bacteria, are alkaline in nature. Skin’s natural acidity neutralizes chemicals and bacteria, a necessary part of the body’s defense system.

The evaluation of tear substitutes

The acid mantle becomes unbalanced with the use of strong alkaline soaps, cleansers, and detergents. Excess perspiration may also affect skin pH. On the other hand, many environmental impurities that settle on or are applied to the skin require cleaners to remove them. Skin cleaners are surface-active substances, primarily detergents and soaps. Soap cleans by acting as an emulsifier; soap allows oil and water to mix so that oily debris can be removed during rinsing. Detergents are primarily surfactants: surfactants are substances that allow or promote “wetting” of a soiled surface and dispersion or suspension (emulsification) of greasy oils in a solution. Surfactants achieve this by reducing the surface tension of the solvent (such as water) or the interfacial tension between two non-miscible liquids such as water and oil. Surfactants can bind to skin keratin, causing protein denaturation, damaging the cell membrane of keratinocytes. This leads to adverse cutaneous responses. Cleaner residues may also be a potential skin irritant, and the alkaline pH of some soap may cause damage to the lipid bilayer of the stratum corneum of the skin causing dryness.²

Depending on the application, cleaners are mixed with builders or pH boosters (such as carbonates, phosphates, silicates), foam boosters, and suitable solvents (such as alcohols or hydrocarbons) to formulate household, industrial, and personal care products.³

Effects on the ocular surface

What is your patient using to clean her skin, particularly around the eyes? What other chemical/soap/disinfectant products is she exposed to at home, on the job, or even in her hobbies? How do the products associated with a patient’s day-to-day activities affect her lid margins and ocular surface? Can these products elicit a chronic response? A careful patient history can tease out potential unrecognized irritants/allergens that can sabotage management of ocular surface disease.

This weekend I carried my handy-dandy pH pencil around with me, testing my skin after contact with various products associated with my week’s-end routine. Although most soaps and body products were slightly acidic, there were instances where my wrist displayed the navy blue color of alkalinity. Keep in mind that although faint, these alkaline products may be aerosolized, create fumes, and can linger on surfaces, including the delicate mucous membranes of the eyes, nose, and throat.

I encourage you to pursue lifestyle questions with your patients, particularly in patients with recalcitrant lid or ocular surface disease. Keep in mind the pH pencil!

Assess dry eye from a systemic standpoint

References

1. Mukhopadhyay P. Cleaners and their role in various dermatological disorders. Indial J Dermatol. 2011 Jan-Feb;56(1):2-6.

2. Bikowski J. The use of cleaners as therapeutic concomitants in various dermatologic disorders. Cutis. 2001 Dec;68(5 Suppl):12-9.

3. Business Dictionary. Definition of “surfactant.” Available at http://www.businessdictionary.com/definition/surfactant.html. Accessed 10/21/ 2014.