Let's try to understand what exfoliation is, why it is good for the skin and how to implement it, with what techniques, what products and with what frequency.
The skin is made up of several layers, the most external being the stratum corneum made up of dead cells, keratinized cells that act as a barrier to the external environment. The stratum corneum is continually renewed through desquamation, a process by which these dead cells detach from its surface. Usually the epidermis is completely renewed every 30 days, but already from the age of 30 this pace of renewal slows down causing, together with other factors, the first signs of aging such as lines of expression, less uniform and dull tone and grain of rougher skin.
Exfoliation works to facilitate this natural epidermal renewal process, helping the "new skin" to come out more evenly. In fact, free from dead cells, the complexion will certainly be more radiant, and it will also receive better all the treatments that normally make up our beauty ritual..
There are two types of exfoliation:
The mechanical exfoliation , as the name suggests, is done with "abrasive" products called scrubs that literally scratch the skin, facilitating the detachment of dead cells by rubbing. Although it is not glass-paper but delicate and balanced products, it is still a fairly aggressive action for the skin and some would do well to avoid it; it is absolutely to be excluded for acneic skin with eruptions in progress, as well as for dry and very dry skin that can at least mix a little scrub with their cleansing oil or delicate cleansing gel, so as to make cleansing also an opportunity for exfoliate the skin.
On the other hand, chemical exfoliation is done with acids, polyhydroxy acids, acid molecules that increase the speed of the cell renewal cycle. In this way it can be scary but it is instead a very delicate exfoliation, more indirect than mechanical exfoliation and recommended for all skin types.
There are three large families of hydroxy acids:
  • the Alpha-hydroxy acids (AHA)
  • Beta-hydroxy acids (BHA)
  • polyhydroxy acids (PHA)

AHAs (among these glycolic, lactic, malic, mandelic acids ...) have great properties in unifying the skin tone and reducing the appearance of wrinkles, so they are generally recommended as anti-aging ingredients for dry skin (yes yes. . we read that right because dry skin is also dry due to an excessive accumulation of keratinized cells that parch the epidermis). In addition, glycolic and lactic acids are two humectants and therefore great moisturizers (to deepen different types of hydration click here). Among the various alpha-hydroxy acids, glycolic is the most powerful and the smallest, in order to penetrate the skin more easily, and for the same reason the most likely to cause adverse effects. Lactic acid is the next in size, more delicate and less prone to causing unwanted reactions in fact we often find it in the formulations of non-exfoliating products to adjust the pH.
BHAs (salicylic acid is the most commonly used in cosmetics) are equally exfoliating acids, the big difference from the previous ones is their ability to literally suck the sebum, so they are highly recommended for oily skin or with a tendency to spots. blacks and acne, as they are able to penetrate clogged pores and remove that excess sebum, as well as having antibacterial and anti-inflammatory properties. People allergic to aspirin (acetylsalicylic acid) would do well to test the product on their arm before applying salicylic acid to their face.
PHAs (such as gluconolactone and lactobionic acid) were the last to arrive and are attributed less irritating properties than their predecessors because they are larger molecules, which certainly penetrate the skin but to a lesser extent, more slowly and less deeply and is for this is what sensitive skin can and should prefer. Thanks to their moisturizing and antioxidant properties, they are the perfect acids for delicate skin, for very mature skin and for all those skin that generally have discomfort or burning with AHA and BHA but do not want to give up chemical exfoliation.
In Korean cosmetics there are many exfoliating products in which we can find the presence of hydroxy acids.
  • Individual exfoliating products such as pads or tissue masks
  • Products for exfoliation cycles such as soaps, toners, serums or creams.
In both cases we are talking about low concentrations, certainly not from professional treatment, which perform their function in the best way over time and can be used without worry at home. Korean cosmetics is characterized by its gentle formulas, with low and very well balanced percentages of acids in which acids are accompanied by moisturizing and soothing active ingredients that allow you to reach the goal of beautiful skin through continuous and constant use.
Let's clear up the first misunderstanding, Korean exfoliating products come proposed for day and night use, but we cover our eyes and ears and pretend we have never received this information. Because?
Exfoliation is certainly good for our face, but when it is performed it is still a "trauma", the skin is deprived of its "defense" component and left at the mercy of external aggressions and oxidative stress. Why exfoliate the skin in the morning and leave the pores beautifully free and open if we then have to fill them with makeup and go out in the smog, smoke and ultraviolet rays? !! It makes absolutely no sense, the ideal is to exfoliate the skin in the evening, and don't forget to apply sunscreen the next day.
In fact, acids are photosensitizers, that is they increase the sensitivity of the skin to light of the sun with the risk of causing spots, so let's use them in the evening, let's not forget the sunscreen the following morning and we avoid acid exfoliation during the summer months. In summer in fact, mechanical exfoliation with scrubs should be preferred.
Normally it is recommended to carry out exfoliation cycles lasting one month in autumn and spring, for these continuous cycles it is advisable to use a product such as a tonic or a serum, but choosing only one exfoliating product to be included in the evening routine, all evenings for a month. 
Many people instead prefer to exfoliate the skin throughout the year, obviously with a different frequency, using products such as pads, masks and scrubs (but also serums ...) one or two, maximum three times a week, always having the foresight to prefer mechanical exfoliation with the arrival of summer.
You can also do both: a continuous cycle of acid exfoliation for a month in autumn and spring and in the remaining months prefer a discontinuous exfoliation.
The important thing is to observe your face, see how the skin reacts and not to give in to the temptation to exfoliate too much and too often because we could cause damage to the epidermis. Among the signals that the skin sends us to make us understand that we are exaggerating with exfoliants appear: redness and inflammation, rashes such as especially small pimples and greater sensitivity to other products of the routine. To restore our skin to a state of well-being, we must stop all foamy cleansers, retinol products and obviously physical or chemical exfoliants. It is advisable to switch to a mild cleanser and a fragrance-free moisturizer.
Extremely red or irritated areas can also be treated locally and desquamate with a rich emollient or an aloe gel and above all have patience because a complete healing can take up to thirty days, or the completion of an entire life cycle of the epidermis cells.