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| Water
in oil |
Oil
in water |
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Emulsions:
(above) the two types of emulsion; (below) an
oil droplet in water, surrounded by a ring of stabiliser
molecules that prevent it from coalescing with its
neighbours. |
Most moisturizers contain
substances called humectants. These are substances
that are capable of attracting water, and which
so help to conserve the water in the skin. One of
the oldest and best examples is glycerine, also
called glycerol. This has been the standard humectant
for many decades and is regarded as completely safe.
Because most cosmetic moisturising products
have a water base they must contain |
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preservatives,
in order to protect them from being contaminated
by bacteria, moulds and yeasts. These micro-organisms
are everywhere, in the environment as well as
on and in our bodies. Without preservatives, micro-organisms
would rapidly spoil the product, and even cause
it to become a health hazard. Well-formulated
products are likely to contain preservatives,
although
only tiny amounts are required. The preservatives
used are all well known and their concentrations
carefully controlled. Parabens are common examples.
Moisturizers for daily use
We have only to look at the cosmetics counters
in the shops to see how many different types of
moisturizer are available. Skilled chemists formulate
these products with care to find the best combinations
for different types of skin and to meet specific
needs. |
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