Lecture
Soaps contain about 80% salts of higher fatty carboxylic acids,
mainly sodium (solid toilet soaps) and potassium (liquid toilet soaps) salts. The use of soap in the form of solutions is increasing. The classic fat composition of the base of toilet soap contains 80-85% rendered beef fat and 15-20% coconut oil. It has been established that soap alters the permeability of skin capillaries. Soap samples containing more than 15% coconut oil cause more pronounced changes, leading to a pre-morbid condition of the skin. This fact is confirmed by many years of clinical
observations by dermatologists, who point to an exacerbation of the process in
dermatosis patients after washing the skin with soap .
A comparison of the effect on the skin of natural fatty acids of different fractional composition contained in soap showed that long carbon chains (C17-C20)
almost never cause disruption of skin capillary permeability, whereas short ones (C10-C16) disrupt permeability. Fatty acids, usually of the
(C10-C16) series, make up 40% of the components of household soap.
All types of soap, when used for a long time, caused mildly pronounced changes in the normal histomorphological picture of animal skin. The changes
were characterized by proliferation of the epidermis and cellular elements in
the upper part of the dermis. In some areas, minor exudative changes were observed (increased skin sensitivity to irritants). An inflammatory reaction was also observed with the use of soap based on a series of fatty
acids (C10-C16), even on areas of skin where the soap was not applied.
After soap treatment of the skin surface, the restoration of its surface pH
(after soap it is usually 7.5-8.0) to normal (7.1-7.5) occurs only after 72 hours. That is, a persistent disruption of the skin surface buffer systems is observed .
Removal of contaminants from the skin using detergents, as
a rule, is accompanied by the simultaneous removal of natural lipids from the
skin surface and a change in its pH. Normally, the skin contains 100-
160 mg/cm2
of lipids. With ordinary washing with clean water, up to 80% of lipids are removed from the skin, and its pH does not change. Detergents with a high
content of fatty components remove lipids from the skin to a lesser extent than
water usually remove up to 97% of lipids. An important characteristic of soap is the time it takes for lipid levels to return to normal after washing. It is
90 minutes for ordinary detergents, and for products with a high fat content –
45 minutes. Thus, for example, out of 41 samples of toilet soap (widely represented
70
in Germany, the soaps of the brands: Clearasil,
Sebamed, Kamil Blue Lotion, Biorence, Donge, Cadum, Fa, Baby Sebamed,
Mira, Palmolive, Roge-Cavailles, Minon, Neutrogena, Emulave remove lipids more strongly (>90%). Skin parameters take quite a
long time to recover (>100 min.) after use
of such soap brands as Kamil Blue Lotion, Kim-beauty Soap, Fa, Biorence,
Cetaphil Lotion, Neca, Silvan, Oilatum, Roc-savon Surgras, Kao, Neutrogena,
Minon .
Propylene glycol is found in a large number of cosmetic products.
It should be noted that it penetrates the skin quite easily. In doing so, it
damages cell membranes, causes rash and itching of the skin. In addition,
propylene glycol is capable of destroying liver and kidney cells, and when
interacting with other components of cosmetic preparations, it can form
carcinogenic compounds.
Lanolin (from the Latin lana – wool and oleum – oil) is wool wax, or
animal wax, obtained by washing sheep's wool.
Lanolin differs from other waxes in its high sterol content
(in particular, cholesterol). Lanolin easily penetrates the skin.
emollient action. It is a thick, viscous mass of yellow or yellow-brown color, with a peculiar odor. At a temperature of 36-42 °C it melts. In
The composition of lanolin contains a great many components. It is a mixture of compounds consisting of esters of 36 fatty acids (myristic, palmitic, ceryl, etc.) with higher alcohols (cholesterol, isocholesterol, etc.) and
free higher alcohols. Lanolin is widely used in various
cosmetic products, most often creams. Lanolin itself has no toxic
effects, but it almost always contains as impurities in its composition
organochlorine, organophosphorus and pyrethroid pesticides. It is precisely the pesticide
impurities in lanolin that cause allergies in consumers when using
creams with lanolin. Highly purified lanolin has no allergenic effect on the human body.
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