We tend to think that substances applied to the skin stay there and only have a local effect. Actually, certain molecules, in particular those that are soluble in lipids, can easily penetrate the epidermis. Once these substances reach the next layer (the dermis), they can be transported into the blood vessels, and from there to the whole body.

When a substance is taken orally, it is absorbed into the blood vessels that run through the intestine. That blood then goes into the liver where molecules are modified and often made inactive. This is called “first pass metabolism”, and is one of the body’s defense mechanisms against offending substances. When a substance is absorbed through the skin, it is not screened by the liver before reaching the rest of the body unaltered. Detergents used in shampoos and baths (see below) can act as “penetration enhancers” and facilitate the absorption of other substances -up to 100-fold- through the skin. (1) (2)

There are good and bad sides to this absorptive property of the skin. Only in the last couple of decades, hormones and drugs have been developed that can be administered on the skin in order to achieve an action somewhere else in the body. Unfortunately, there are also a number of publications in the medical literature in which a substance thought to be innocuous has caused serious adverse effects. For instance, hexachlorophene was once used in hospitals to cleanse the skin of newborns with the idea of preventing life-threatening infections…until a group of astounded physicians proved the relationship between a devastating neurological disorder in premature babies and the excessive absorption of the antiseptic through the intact skin. (3)

Many cosmetics are emulsions of oil in water or water in oil, or even pure oil, making them the perfect vehicles for substances that could then be absorbed through the skin. It would be wise to avoid chemicals known to be dangerous and to favour the use of substances known to be beneficial, wouldn’t it? Lavender for instance, has traditionally been used in baby skin care. It has a local effect, stimulating cellular division, which promotes rapid healing; it acts as an anti-inflammatory and has a soothing, balancing effect on the skin. But it also has a general effect, alleviating stress and anxiety, and thus is an excellent relaxant.



ARE BABY PRODUCTS GENTLER?

There is an enormous range of baby products available in the market. Advertising suggests that the ingredients in those products are milder, gentler than those used in adult cosmetics. Unfortunately, this is often not true. Just recently, I closely examined the ingredients in a leading brand of baby shampoo. The ingredients are very similar to other common shampoos that do cause tears and I must say I have not yet found an explanation for the difference.

The fact is that tears are important in that they are the body’s way of washing off irritating substances from the eyes, substances that should be kept away from the eyes in the first place. Most baby shampoos these days are based on Sodium Laureth Sulfate as their surfactant (that is what makes them foam). This chemical is a moderate to harsh skin irritant, and the manufacturers recommend avoiding contact with the eyes. It is also an effective penetration enhancer and it can allow other, more dangerous molecules, to easily penetrate the skin. (2) (4)

For instance, Sodium Lauryl Sulfate (SLS), one of the most widely used chemicals in a large variety of shampoos, foaming baths, liquid soaps and toothpastes. The pharmacological industry uses it as a penetration enhancer, to facilitate the absorption of drugs through the intestines or the skin. It is well known to denature proteins (that is, alter their structure) (5). Due to this, some scientists worry that SLS could cause damage to the cornea when it comes in contact with it. SLS is the skin irritant par excellence; it is, in fact the most widely utilized model for studying skin irritation both in laboratory models and in people (6) (7). In one study involving children, even very low concentrations of SLS (0.5% water solution) provoked serious changes of the skin’s barrier function (8). Considering that in labels, ingredients ought to be written in order of quantity and SLS is usually the second or third ingredient after water, one wonders what sort of skin damage occurs at these concentrations.

Baby products can also suffer from a genuine attempt to make them safer. In the European Union, where regulations are stricter than in New Zealand, toiletries for children are required to contain 50 times fewer microbes than products for older children and adults. This is a well-intentioned precaution, because as their immune systems are not well developed yet, babies are less prepared to fight infections. This also means these products contain higher concentrations of preservatives to maintain microbe levels that low.



WHAT ABOUT PRESERVATIVES?

Unfortunately, preservatives are unavoidable for any water-containing product that is expected to sit on a shelf for more than a few days. Microbes thrive in water; any cosmetic containing water (such as lotions and creams) is therefore prone to grow yeasts and bacteria without the presence of a preservative and would be extremely dangerous to apply to the skin. Most preservatives carry reports of nasty side effects as they are dangerous by their very nature…their function is to kill cells! The preservative with the worst press is probably parabens, which is largely used in cosmetics and even foods, as it has been linked to cancer (9).

You might find that some of your skin products contain no preservatives. Cosmetics and toiletries containing oils only do not require preservatives as microbes cannot live in oil alone. They do require antioxidants, as oils spontaneously become oxidized when exposed to air, and this is where tocopherol (vitamin E) finds its place.



ARE NATURAL PRODUCTS ANY BETTER?

Nature seems to be an excellent chemist. Plant extracts contain a mix of hundreds of different molecules that often have synergistic and complementary actions. Most herbs used in cosmetics are known to have beneficial effects on the skin and in the whole body, thanks to the skin’s absorption capacity. And don’t forget…natural substances have been used for centuries, both for medicinal purposes and in skin care, so “surprise” adverse effects are less likely to occur.

Scientists spend years in the laboratory, developing or isolating molecules know to have certain beneficial actions. Unfortunately, they can not see the big picture. They can only focus only on their area of expertise and ignore other biochemical pathways in which a molecule could participate. This results in products that have only a very specific, local action, without the benefits of a more holistic approach, and sometimes cause nasty reactions on the skin or somewhere else in the body.

Usually, herbalists create formulas in which each ingredient has a particular function related to the customer’s health. One ingredient might be regenerative, emollient and toning, another might relieve itching, dryness or inflammation, and another might have an uplifting effect on emotions. Mainstream products are formulated differently: one ingredient might be moisturising, but then next one is used to stabilise the emulsion, another one to improve the “feel” of the lotion on the skin, and the other is added to improve the texture. It’s all about the customer’s perceptions, not real benefits.

If you decide to go the natural way, make sure that you read the label, because there are no regulations with regards to labeling a product as “natural”. Looking at the label of a “herbal” shampoo, it contains 27 ingredients, of which only 2 are natural, and they are towards the end of the list; the rest is synthetic. You will identify natural ingredients because they carry a Latin name, e.g. Simmondsia chinensis, Matricaria recutita. Chemical names are unpronounceable, e.g. methylchloroisothiazolinone, guar hydroxypropyltrimonium chloride.



ANY RECOMMENDATIONS?

A relationship has been found between “very clean” countries and high rates of asthma and atopic dermatitis. Doctors have attributed this to a lack of exposure to environmental antigens, that is, particles that stimulate and help mature the immune system. However, people in these nations also use large quantities of toxic toiletries and household cleansers.

Don’t overdo it. Don’t wash off your baby’s natural skin oils with detergents, only to replace them with artificial ones, and don’t irritate his skin with harsh cosmetics. Sure enough, in our civilized world, we want to keep ourselves clean and smelling good, but use only the few products you absolutely need, and then only use the safest, gentlest formulas.

Very gentle, natural soap, mild shampoo and some butt balm is all a baby needs. I also recommend massaging babies with natural oils, because they enjoy the touch and they relax better before they go to sleep. Babies love their bubble bath, but save it for special occasions; don’t let them linger in it and rinse them well before drying. Also avoid artificial fragrances and colours as they are major triggers for reactions.



REFERENCES

(1) Karande P, Jain A, Mitragotri S. Discovery of transdermal penetration enhancers by high-throughput screening. Nature Biotechnology 2004; 22:192-197.

(2) Corazza M, Virgili A. Allergic contact dermatitis from ophthalmic products: can pre-treatment with sodium lauryl sulfate increase patch sensitivity test? Contact Dermatitis 2005 May; 52(5): 239.

(3) Pratt, William B, Taylor P. Principles of Drug Action. The Basis of Pharmacology. Churchill Livingston 1990. 209.

(4) National Occupational Health and Safety Commission. National Industrial Chemicals Notification and Assessment Scheme. Full Public Report. MIPA-Laureth sulfate. Canberra 2004: 7-9.

(5) Ananthapadmanabhan KP, Moore DJ, Subramanyan K, Misra M, Frank M. Cleansing without compromise: the impact of cleansers on the skin barrier and the technology of mild cleansing. Dermatologic Therapy Feb 2004. Vol 17:16.

(6) Lee CH, Maibach HI. The sodium lauryl sulfate model: an overview. Contact Dermatitis 1995 Jul;33(1): 1-7.

(7) Zhai H, Fautz R, Fuchs A, Branco N, Maibach HI. Assessment of the Subclinical Irritation of Surfactants: A Screening Open Assay Model. Exogenous Dermatology 2002; 1:238-241.

(8) Zahejsky J, Vasku V, Rovensky J. Objective assessment of the effect of sodium lauryl sulfate on the surface of the skin in childhood. Derm Beruf Umwelt 1987 Jul-Aug;35(4):133-6.
(9) Harvey PW, Darbre P. Endocrine disrupters and human health: could oestrogenic chemicals in body care cosmetics adversely affect breast cancer incidence in women? J Appl Toxicol. 2004 May-Jun;24(3):167-76.

April 11, 2006