What is hidden behind the PP(-) skin type classification?

The first letter "P" indicates that skin aging is well established. On mature skin, after the age of fifty, expression lines that appeared earlier (crow's feet at the corners of the eyes, frown lines...) become increasingly pronounced, with loss of firmness being the cause. Cellular degeneration continues, coupled with a reduction in the number and size of fat cells in the fatty tissue of the hypodermis, the deepest layer of the skin. This decrease leads to a loss of volume and firmness, which will hollow out the cheeks.

Furthermore, in women, during menopause, deficiencies in estrogen and progesterone exacerbate the chronological aging of the skin. Indeed, estrogens stimulated keratinocytes, the synthesis of hyaluronic acid and collagen, and inhibited the growth of hair follicles. However, with this abrupt drop in the secretion of female hormones, we observe an increased skin dryness, a modification of the barrier function, and a loss of radiance.

The letter "P" signifies that the skin is well protected against the sun's UV rays. Beyond their beneficial effects on mood or vitamin D secretion, excessive sun exposure is the main cause of premature skin aging and the onset of skin cancers. Indeed, UVA rays can cause dermal changes , especially in elastic tissue, and UVB rays can lead to epidermal damage. Activation of free radicals, alteration of the cell membrane, DNA modification... UV rays act differently within skin cells to generate damage, which can alter the cell's function, cause its death, or provoke DNA mutations that eventually lead to the formation of cancerous cells. Thus, even though the skin has some defenses against UV rays (melanogenesis, endogenous antioxidant system...), it is important to regularly and adequately apply a sunscreen product suited to one's phototype and sun exposure conditions for reasonable exposure while limiting risks.