Cosmetic Chemistry & Electrical Modalities
Roughly ten percent of the exam covers what is in the products you apply and what the machines in the treatment room actually do. You do not need to be a chemist, but you do need to read a label intelligently, understand what pH means for an exfoliating product, recognize the difference between a humectant and an occlusive, and know precisely who should not receive an electrical treatment. Contraindications for electrotherapy are among the most reliably tested points in this section because the consequences of getting them wrong are medical rather than cosmetic.
pH, Emulsions, and Product Structure
The pH scale runs from 0 to 14, with 7 neutral, values below 7 acidic, and values above 7 alkaline. It is logarithmic, so each whole number is a tenfold change: a product at pH 3.5 is roughly a hundred times more acidic than one at pH 5.5, which is why small numeric differences on an exfoliant label matter a great deal. Healthy skin sits at a mildly acidic pH of about 4.5 to 5.5, and highly alkaline products disrupt that acid mantle. Most creams and lotions are emulsions, mixtures of oil and water held in suspension by a surfactant or emulsifier. Oil-in-water emulsions have water as the outer phase and feel lighter, while water-in-oil emulsions have oil as the outer phase and feel richer and more occlusive. Without an emulsifier the two phases separate. Understanding this structure explains why one moisturizer feels weightless on oily skin and another feels appropriate on very dry skin.
Active Ingredients and Allergic Reactions
Humectants such as glycerin, hyaluronic acid, and sodium PCA attract and bind water in the stratum corneum, which is what dehydrated skin needs; in dry air they work best sealed in by an emollient or occlusive. Alpha hydroxy acids such as glycolic and lactic acid are water-soluble and act mainly at the surface, loosening the bonds between dead cells, while salicylic acid, a beta hydroxy acid, is oil-soluble and can travel into sebum-filled follicles, which is why it suits oily and acne-prone skin. Both increase photosensitivity, so daily sun protection is mandatory alongside them. Not every reaction to a product is an allergy: irritant contact dermatitis appears quickly and is dose-related, while allergic contact dermatitis is a delayed immune response that typically appears about a day later as itching, redness, and small bumps confined to the application area. The response to a suspected allergy is to stop the product, record the ingredient list in the client's file so it is avoided in future, and refer to a physician if symptoms persist.
Electrical Modalities Used by Estheticians
Galvanic current is a constant direct current used two ways: desincrustation, which uses the negative pole with an alkaline solution to saponify sebum and soften follicular debris before extraction, and iontophoresis, which uses matched polarity to drive water-soluble products into the skin. High frequency produces a mild germicidal and drying effect on intact skin and is used in direct and indirect applications; because the electrode produces a spark, all alcohol-based and flammable products must be cleared from the area first. Microcurrent delivers a very low level current used for toning and stimulation. LED light therapy is non-thermal and non-ablative, with blue wavelengths commonly directed at acne-causing bacteria and red wavelengths used to stimulate and calm; it is not a laser, and lasers are outside esthetic scope in California entirely. Eye protection is used with LED and with magnifying lamps.
Contraindications and Electrical Safety
Electrical modalities share a common list of contraindications, and the exam expects you to decline rather than to reduce the setting. A cardiac pacemaker or other implanted electrical device rules out galvanic, high frequency, and microcurrent entirely, because of the possibility of interference. Pregnancy, epilepsy or a seizure disorder, active cancer without physician clearance, metal implants in the treatment area, open or broken skin, and any loss of skin sensation are also contraindications. High frequency is additionally avoided for clients with asthma triggered by ozone, and LED is avoided for clients on photosensitizing medications or with certain eye conditions. In every case the correct answer is to offer a non-electrical alternative such as a manual facial; lowering the intensity, restricting the area, or obtaining a signed waiver does not eliminate a medical contraindication. General electrical safety completes the picture: inspect cords for damage, use one appliance per outlet, keep cords out of walkways, never handle a plugged-in device with wet hands, unplug by grasping the plug rather than pulling the cord, and unplug equipment when it is not in use.
Last updated: July 2026