06 Understanding the Phenomenon of Moisturizing

WATER HYDRATES

Water has a major role in the functioning of living organisms, it gives the skin its suppleness and elasticity. The water present in the epidermis is not evenly distributed. The hydration of the skin is one of the factors responsible for resistance to mechanical stress.

Drier skin will therefore "break" more easily (think of the wounds that appear on the hands when it is very cold). If the stratum corneum is not properly hydrated, the skin will be less resistant and less stretchy.

In addition, the water present in the stratum corneum regulates the normal desquamation process. Poor hydration results in the presence of dandruff.

The water content of the basal epidermal layers is 65 to 70%. The further up the surface layers, the lower the water content to only 10% in the stratum corneum. The water present in the stratum corneum allows the smooth functioning of the enzymes allowing desquamation.

INSENSIBLE WATER LOSS (IWL)

IWL is the water that rises gradually to the skin surface and passes through the skin from the inside to the outside. Perspiration can do it; it is then an active IWL. Dogs and cats sweat very little, so this is not the way their IWL works. It is almost exclusively by diffusion through the stratum corneum (passive IWL).

There is therefore a difference in hydration between each side of the epidermis. The outer face in contact with the external environment is drier. The drying of the stratum corneum due to the external elements causes the rise of the water towards the superficial layers and the IWL. An increase in IWL results in an alteration of the skin barrier.

The higher the IWL, the less the skin is hydrated and vice versa. In older animals, IWL is low and hydration is low, so there is not enough water flowing to the epidermis. In neonates, on the other hand, the IWL is very high, and the hydration is very high, so there is a strong fixation of the water but also an excessive loss of water.

Note: it is impossible to have a healthy puppy with dry skin. It can be as simple as the puppy does not drink enough or it can be a much more serious underlying issue.

IWL also depends on environmental factors such as humidity. If the humidity is 100% then the IWL is at 0. The movements of the air drying the skin are also an important environmental factor.

There are also individual factors such as age, sex, race, skin colour (because melanin acts on water retention), anatomical site, body side, sweating, etc.

The temperament of the animal also plays an important role. Studies have shown that the calmer a dog is, the weaker his IWL is.

Clipping also has a strong impact on the IWL because the hairs help retain water and increase the temperature of the skin surface. The IWL would therefore decrease after clipping returning to normal after 48 hours when the clipping was not irritating.

If clipping has been irritating, IWL increases due to alteration of the skin barrier.