You may be wondering how certain chemicals from toiletries applied to the skin, hair and teeth are able to find their way into the body where they have the potential to cause long term damage to health. Hopefully, this mini biology lesson will help you to understand the basics.
So, how do these chemicals get into the body?
Surprisingly, they are able to pass into the body through our skin.
The skin is the body's largest organ accounting for 16% of body weight. It is comprised of 3 layers – Epidermis, Dermis, and Hypodermis.
Epidermis – is where skin cells are produced. The new ones form at the base and gradually push the older ones upwards where they become drier and flatter as they near the surface. At the base, the cells consist of 75% water which reduces to 1% at the surface where they shed.
Dermis – consists of:
Hair follicles where each hair forms.
Sebaceous glands which secrete oil to prevent dryness.
Sweat glands which secrete water and salts and help to keep the skin cool through evaporation of sweat on the skin surface.
Arrector Pili muscles which draw up the skin surface when we feel cold (goose pimples), making the surface area smaller to conserve body heat.
Blood vessels which help to nourish the skin and transport substances of a low molecular weight to the rest of the body.
Nerve Fibres which provide the sense of touch
Hypodermis – which is a layer of adipose (fatty) tissue.
Until quite recently, scientists believed the skin was a total barrier. They now know that it allows substances of a low molecular weight through.
If you think of the skin as a mesh like a tennis racquet, as in the diagram opposite, you will see how some molecules can pass through and others cannot.