Soaps and cleansers

Author: Dr Amanda Oakley MBChB FRACP, Dept of Dermatology Waikato Hospital

Why wash?

Everyone likes to feel clean; it's refreshing, invigorating, relaxing and enjoyable. Washing your skin removes excessive oil and unpleasant odours as well as make-up, sunscreens and dirt.

How to wash: wet your skin. Apply soap or cleanser to your hands, add warm water and work into lather. Massage gently. Rinse thoroughly. Gently pat dry.

Do I have normal, dry, oily or sensitive skin?

These terms are most frequently applied to facial skin, but may apply to other sites as well. To determine your skin type, wash your face and pat dry. Wait for an hour, then press a tissue to your forehead, cheeks, chin and nose. If your face is not shiny and there's no oily residue on the tissue, you have normal skin. If your face looks/feels tight or is flaky and there is no oily residue on the tissue, you have dry skin. If your face is shiny and the tissue reveals an oily residue, you have oily skin. Many people have combination skin: the T-zone (forehead, nose, chin) is oily but the cheeks are normal or dry.

Normal skin has a correct balance of moisture and oils. It is slightly acidic at a pH of 4.5-5.75 (6.5 under your arms). A variety of harmless (commensal) bacteria and yeasts live in low numbers on the skin surface, and may help protect your skin from infection (invasion by more harmful bacteria such as staphylococcus or streptococcus).

Sensitive skin is skin that stings easily, especially during or just after cleansing. Sensitive skin is more likely to be dry and is hyper-reactive, i.e. prone to develop dermatitis (itchy bumpy skin). Sensitive skin may be inclined to be red, flush easily or have broken capillaries (telangiectasia).

There is often an underlying skin problem such as:

Oily skin, or seborrhoea, predisposes to acne. If you have an oily complexion, you may be tempted to scrub twenty times a day: don't! You might dry your skin too much and rather than preventing infection, you may even increase the number of harmful bacteria. Just gently wash affected areas when you wake up, post-exercise and at bedtime.

What cleanser should I use?

Pure water alone is not quite enough: removing dirt, which is fat-soluble (lipophilic) and sticks to the skin, requires a surfactant.

Surfactants are active cleansing substances that consist of a fat-soluble (lipophilic) part and a water-soluble (hydrophilic) part. The lipophilic part sticks to oil and dirt, and the hydrophilic part allows it to be washed away. Surfactants may be a soap, a synthetic detergent or a combination The choice of cleaning agent helps determine the product's lathering characteristics, feel on the skin and how easily it rinses off.

There is a wide range of products designed for washing, available as bars, liquids, gels, creams, shampoos, scrubs, masks, cloths and wipes. Manufacturers consider mildness, biodegradability, low toxicity, cleansing ability, emulsification, moisturization, skin appearance and feel, smell (fragrance) and lubrication to be important aspects of their products.

Cleansers may contain:

What are the complications of skin cleansing?

Soaps and cleansers can irritate and result in skin problems. These are rare with modern synthetic detergent products made by reputable manufacturers, if they have been designed for sensitive skin and are used appropriately. Over-washing may have the following effects:


Soap has been made since ancient times, but has been particularly popular for cleansing the body since the mid-eighteenth century when modern manufacturing processes were discovered.

Soap is an anionic surfactant. Soap is made from fats and oils mixed with alkali, forming glycerine and the sodium salt of the fatty acid. The fats required for soap making come from a combination of tallow, grease, fish oils, and/or vegetable oils. In ancient times, the alkali came from ashes but today the alkali for soap formed into solid bars is sodium hydroxide. Liquid soaps are made with potassium hydroxide.

The hardness, lathering ability, and transparency of soap vary according to the combination of ingredients.

Disadvantages of soap


Synthetically produced detergents (syndets) were developed in the 1950s and are widely available. They are made from a variety of petrochemicals (derived from petroleum) and/or oleochemicals (derived from fats and oils). These hydrocarbon chain sources are used to make the lipophilic end of the surfactant molecule. Chemicals, such as sulphur trioxide, sulphuric acid and ethylene oxide, are used to produce the hydrophilic end of the surfactant molecule.

Compared with soap:

Hypoallergenic products

The manufacturers of hypoallergenic skin cleansers have tried to avoid using substances that are likely to cause contact allergy. Their products are often "fragrance-free" (low levels of masking fragrances are permitted), "mild" and "non-irritating". If you have acne, choose products that are labelled as "oil-free" and "non-comedogenic".

However, even hypoallergenic products may still be irritating to those with very sensitive skin, and they may still rarely cause contact allergy.

Labelling in the USA

For the US, the FDA states: "If a cosmetic claim is made on the label of a "true" soap or cleanser, such as moisturizing or deodorizing, the product must meet all FDA requirements for a cosmetic, and the label must list all ingredients. If a drug claim is made on a cleanser or soap, such as antibacterial, antiperspirant, or anti acne, the product is a drug, and the label must list all active ingredients, as is required for all drug products."

There are no specific labelling requirements in New Zealand.

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