Abstract:
Almost every person will experience dry skin during his or her lifetime. Many
people experience occasional episodes, but some have a chronic problem with
xerosis that is irritating and troublesome. Moisturisers are the mainstay of
treatment for dry skin, daily maintenance of normal skin, and adjunctive therapy
for many skin diseases (Flynn et al., 2001:387).
The objectives of this study were the formulation and evaluation of urea
containing products. Seven different cosmetic products were formulated: hair
gel, shampoo, facial toner, facial cleanser, day cream, foot and heel balm and a
body cream. The product development program started with a pre-formulation
study, followed by formulation of the seven skin care products, which were
followed by stability testing, based on the requirements of the South African
Medicines Control Council (2003:21, 22, 23) for new products. The stability of
all skin care products must he matched to the expected period of usage by the
consumer, as well as to the user's requirements. The formulations were tested
under ICH conditions (accelerated stability studies) over a period of three
months at three different storage temperatures, i.e. 5"C, 25"C/60%/RH,
40°C/75%RH. Stability indicating tests that applied to these formulations, were
conducted: pH, relative density, viscosity, appearance, penetration, spreadability,
assay of urea, the assays of the preservatives and the release study of urea by
means of membrane release.
Chapter 1 gives a literature overview of the skin and the properties and uses of
urea. Chapter 2 deals with the formulation of the urea products and the chemicals
that have been used. Chapter 3 describes the methods used for accelerated
stability testing. Chapter 4 finally deals with the results obtained and the
conclusions that were made.
The test results showed the following: There was a prominent change in the pH
of all the formulated products, this can be due to the decomposition of urea into
carbon dioxide and ammonia (Beiersdorf, 2003). Higher temperature and
moisture increase this decomposition and cause the pH to increase to values as
high as 9 (Anon, 2003:20). However, urea compositions can be stabilised when
they contain methylsulfonylmethane (MSM) (Herschler, 1981:l).
The viscosity, spreadability, penetration, relative density and appearance of the
products remained more or less the same over three months, except for the day
cream and the facial cleanser where phase separation occurred after 1 month. The
urea content decreased with time, but only dropped to below 90% in the day
cream after 3 months at 4O0C/75% RH. HPLC analysis of the preservatives
confirmed their stability in the formulated products. The preservative efficacy
results proved that the products were sufficiently protected from microbial
contamination.
The release study indicated that urea is released at a steady rate from the
preparations tested. The release of urea from the hair gel is about four times
faster than that from the body cream and the foot and heel balm. In general, the
release is influenced by the viscosity of the medium and should be faster from
the gel than from the creams (Shah et al., 1991:55).
In conclusion it can be said that urea was successfully formulated into the seven
cosmetic products except for the facial cleanser and day cream which must be
stabilised.
