Author: Dr Amanda Oakley MBChB FRACP, Dept of Dermatology Waikato Hospital, 2002.

What are shampoos?

Shampoos are cleansers designed to clean your hair and your scalp. Most shampoos clean your hair very well. Where they differ is how your hair feels afterward, depending partly on the strength of the surfactants. Stronger clarifying shampoos should not be used more than once or twice a week. Those designed for daily use contain mild surfactants and are less likely to irritate the scalp.

Ingredients of shampoos

All shampoos are 80-90% water with 2-8% detergents and foaming agents and about 1% fragrance and preservatives. Shampoos often contain antistatic and detangling agents as well as thickeners, humectants, sequestering agents, colour and conditioners.

Effective detergents include sodium lauryl sulfate, laureth sulfate and sulfosuccinate. They give the hair a squeaky clean feel.

Clarifying shampoos contain heavy-duty surfactants. Body building shampoos contain proteins that bond to hair and increase its volume.

Moisturizing shampoos are the best choice for dry, flyaway hair. They can cut down on static, make split ends look better (by gluing them together with proteins), and pull moisture onto hair to keep it from getting too dry.

Revitalizing or replenishing shampoos are made for color-treated, permed, and damaged hair and contain gentler surfactants. They may include ingredients designed to retain colour or to help to repair split ends, but there's little evidence that they are effective.

2-in-1 shampoos with conditioner save time but may leave your hair feeling too dry or sticky.

Baby shampoos contain amphoterics and have less detergent and are not designed for cleaning adult hair, especially when alot of styling products have been used. They may be appropriate for someone that has damaged hair and who finds standard shampoos too harsh.

How to use a shampoo

Wet the scalp and hair using warm or cool water (hot water can be drying to the hair and scalp). Apply a 5 to 10-cent amount of shampoo to palm and rub hands together to evenly distribute. Apply the shampoo to the scalp. Massage gently with your fingertips for about 30 seconds and then rinse thoroughly.

You only need to lather your hair once under normal conditions. Lather is destroyed by sebum so an oily scalp may require a second shampoo. Excessive lather is wasteful: it doesn't clean hair any better. Shampoo should be easy to rinse off, but conditioners, styling products and chemical processes may leave a residue.

After rinsing, apply some conditioner in one hand and rub palms together to evenly distribute. Apply conditioner from the middle of the hair shaft down to ends. Avoid the scalp unless scalp is dry. Comb conditioner through hair to distribute product evenly. Leave conditioner on hair for a few seconds to help smooth the cuticle. Rinse thoroughly.

Conditioners are designed to counteract the effect of detergents, repair static electricity and split ends. A silicone film smoothes cuticles and reduces friction and hair breakage, and maintains colour. Conditioners often contain anionics for softness and manageability.

Medicated shampoos

Medicated shampoos may contain salicylic acid to loosen flakes of skin, and selenium sulfide, zinc pyrithione, ketoconazole or ciclopirox to reduce the numbers of Malassezia yeasts on the scalp. They are very helpful in dandruff and seborrhoeic dermatitis. They may also help treat scalp psoriasis and atopic dermatitis, but often shampoos containg coal tar are more useful in these conditions.

Medicated shampoos need to be left on for longer than normal shampoos. Ideally, make the hair wet 10 minutes before your shower/bath. Apply medicated shamoo as above. and massage gently into the scalp. Leave for 10 minutes and rinse off well.

You may still use a conditioner afterwards.

Skin problems due to shampoos

Shampoos can irritate and cause scalp problems. These are rare with modern products made by reputable manufacturers if they have been designed for sensitive skin and are used appropriately. Overwashing may have the following effects:

Hypoallergenic products

The manufacturers of hypoallergenic shampoos 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 oily skin (seborrhoea), choose shampoos designed for your skin type.

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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