What Are Medicated Shampoos?
These deserve a particular mention as generally they are used far too widely and indiscriminately. They fall into three categories.

Firstly tar shampoos, which can be made from varying fractions of either coal tars or wood tars. There is some concern that the long term use of coal tar shampoos can be carcinogenic. Tar shampoos are usually helpful in the treatment of dry, scaly or itching conditions of the scalp and may be used preferably as short term measures in helping to treat simple scurf or dry dandruff, psoriasis and certain types of neurological eczema. Tars are not easily soluble however and some of the bases for these may be too drying for the scalp. Also, the main objection to their use is the smell. Wood tars are usually therapeutically more efficient and have aromatic smells less reminiscent of the road-menders tars than coal tar.

Modern dandruff shampoos contain as active ingredients either selenium sulphide which is a chemical irritant and poison or zinc or zirconium pyrithione or omadine salts. As these all tend to have an irritant action on the scalp, they may cause a greater production of scalp oil making the hair become oily more rapidly. This is rarely stated on the label. They are better used with caution and it is never a good practice to use any medicated compounds on the scalp over a long period without good reason and certainly not as a palliative to prevent problems.

Hair and skin cleansers such as cetrimide can be very useful as they are often very efficient skin-antiseptics. They rarely cause irritation and leave the hair feeling very silky. Care must be taken however to avoid contact with the eyes.

Contrary to popular opinion baby shampoos are not necessarily milder or more gentle in their cleaning action than other shampoos. The major difference is that they have to conform to a number of legal requirements in most countries. Babies have a far larger skin area in relation to bodyweight than adults so these shampoos may not contain any ingredients which could cause harm if absorbed by the skin. The other major requirement is that they may not cause damage to the conjunctive membrane of the baby's eye.

Many of the shampoos available today are marketed as being P.H. balanced. Some companies make this a particular selling point for their products. The term P.H. refers to percentage of hydrogen which is used on a scale of 1-14. Acid solutions are from 1-7, 7 is neutral and alkaline solutions are 7-14. Normal skin is slightly acid having a P.H. value of about P.H. 5.4-5.6.

Permanent waving lotions and straightening creams have a P.H. value of up to 9.6 which his very alkaline. Products stronger than this are illegal in many countries as they are likely to cause skin irritation and chemical burning. Alkalies cause the hair to swell and loosen the cuticle cells. Acidic compounds have the opposite effect but if too strong the hair will become hydrolysed and made more brittle and less elastic with the consequent likelihood of breakage.

Conditioners are usually slightly more acidic than shampoos to counter the effects of hairdressing chemicals. In most cases however the scalp will return to its normal slightly acid level within a half hour but the hair can be greatly affected for good or ill.

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