The different types of wrinkles.

The wrinkles represent one of the most visible signs of cutaneous ageing. They correspond to structural modifications of the skin, manifesting as folds and grooves of varying depth on its surface. These alterations stem from a progressive evolution of the different layers of the skin, and in particular the dermis. Indeed, with age, the number and activity of fibroblasts, the cells responsible for synthesising the fibres of collagen and elastin, ensuring skin suppleness and elasticity, progressively decline. Furthermore, at the epidermal level, keratinocytes divide more slowly over time, leading to a gradual thinning of this protective layer. Thinner skin becomes mechanically more vulnerable and less able to withstand repeated stresses. This is compounded by a reduction in adipose tissue, namely the hypodermis, which normally contributes to supporting facial volume.

The wrinkles are not, however, solely a consequence of the skin’s intrinsic ageing. Several mechanical and environmental factors contribute to their formation and deepening. The constant pull of gravity exerts continuous stress on the skin’s tissues, promoting gradual sagging. Repeated positional pressures, particularly those applied to the facial skin during the sleep, can also leave lasting impressions on certain areas. Repetitive facial movements, resulting from muscle contractions during expressions, impose constant mechanical stress on the skin. Finally, the oxidative stress, partly driven by UV exposure, accelerates skin ageing.

Various classifications of wrinkles have been proposed in the scientific literature, enabling a better understanding of their origin, evolution and characteristics.

Among the various methods for classifying facial wrinkles, the distinction between dynamic and static wrinkles is one of the most widely used in dermatology and aesthetic medicine. This classification is based on the role of muscle contraction in the formation of wrinkles and allows us to distinguish those that appear during facial movements from those that remain permanently visible, even at rest.

Expression wrinkles, also known as dynamic wrinkles.

Expression lines are generally the first to appear on the face. From about the age of 30, the production of collagen and elastin begins to decline gradually at a rate of around 1% per annum, reducing the skin’s capacity to withstand mechanical stress. In this context, the repeated movements involved in facial expressions play a key role in the formation of these lines. Each smile, furrowed brow, squint or clenched jaw causes a transient deformation of the skin. With repeated activation, the skin progressively loses elasticity and eventually folds repeatedly in the same areas. At first, these lines are only visible during movement and disappear when the face is at rest.

Depending on their location, several types of expression wrinkles can be distinguished:

• Forehead wrinkles, which take the form of horizontal lines appearing when the eyebrows are raised.

• Glabellar wrinkle, also known as the interbrow wrinkle or glabella wrinkle, corresponding to vertical or horizontal furrows between the eyebrows, associated with the contraction of this region.

• Bunny lines, or witch’s lines, localised on the lateral and superior borders of the nose, resulting from the contraction of the levator muscles of the nasal ala and upper lip.

• Crow’s feet wrinkles, or periocular wrinkles, located at the outer corner of the eyes. They are among the first visible wrinkles, notably due to the particular thinness of the skin of the eye contour, four to five times thinner than that on the rest of the face, and a high number of daily blinks.

Static wrinkles, also referred to as age-related wrinkles.

Static wrinkles typically emerge at a later stage and remain visible even when the face is at rest. They primarily result from the structural ageing of the skin, marked by a gradual reduction in the dermal support proteins. These wrinkles can occur across the entire face, as well as on other areas of the body. Among the most common static wrinkles are:

• Nasolabial folds, which extend from the wings of the nose to the corners of the mouth and often indicate a gradual sagging of the cheek.

• Solar plissé wrinkles, also called smoker’s lines or barcode lines, situated vertically above the upper lip.

• Marionette lines, or labio-mental grooves that run from the corners of the mouth to the chin and give a drooping appearance to the lower face.

• Wrinkles of the neck and décolletage, often horizontal, sometimes referred to as Venus rings, related to the loss of subcutaneous adipose tissue and underlying bony changes.

Note : Some static wrinkles can also be influenced by sleeping habits. Sunlight is also a major factor in accelerating static wrinkles because UV radiation produces free radicals that fragment and disorganise the collagen and elastin fibres.

Beyond the distinction between dynamic and static wrinkles, some scientific classifications rely on the morphological aspect of wrinkles, which allows for a better understanding of why some wrinkles remain fine and superficial, while others become deep and persistently marked, regardless of facial movements.

Superficial atrophic wrinkles.

Superficial atrophic wrinkles appear as fine, shallow lines—often multiple—that give the skin a creased appearance. They are primarily related to a progressive thinning of the skin, both in the epidermis and in the superficial dermis. These wrinkles are commonly observed in areas where the skin is naturally thinner or more exposed to external aggressors. They may be exacerbated by reduced skin hydration and by an alteration of the natural moisturising factors.

Deep elastotic wrinkles.

Deep elastotic wrinkles are characterised by pronounced, long-lasting folds associated with significant alterations in the extracellular matrix. They are closely linked to photoageing, that is, ageing caused by chronic exposure to sunlight. Unlike superficial wrinkles, deep elastotic wrinkles reflect permanent damage to the skin’s supporting structures.

Gravitational folds.

Gravitational folds correspond to skin depressions caused by the gradual sagging of tissues, under the combined effect of gravity and the loss of structural support. They are not the result of simple muscle contraction, but rather a redistribution of facial volumes due to the decrease in collagen, elastin and subcutaneous adipose tissue. These folds reflect an overall mechanical imbalance whereby the skin and underlying tissues can no longer effectively resist gravitational pull. They present as broad, deep furrows.

This classification of wrinkles is based predominantly on their appearance and structure.

The etiological classification of wrinkles is chiefly concerned with their principal cause, rather than with their appearance or behaviour during facial movements.

Wrinkles associated with cutaneous atrophy.

Some wrinkles originate in a progressive atrophy of the skin, characterised by a decrease in the thickness and density of the skin tissues. This phenomenon is linked to a slowdown in cell renewal, reduced fibroblast activity and a loss of extracellular matrix components. The skin then becomes more fragile, less resistant to mechanical stress and more prone to visible lines. These wrinkles are part of the skin’s intrinsic ageing process.

Dynamic and static expression wrinkles.

As mentioned earlier, certain wrinkles are associated with the facial muscle activity. Dynamic expression wrinkles initially emerge from repeated contractions of the facial muscles, whereas static expression lines represent the gradual fixation of these folds over time. This progression reflects the skin’s reduced capacity to deform and subsequently return to its original shape.

Wrinkles associated with skin laxity.

The wrinkles associated with skin laxity are primarily caused by an alteration of the skin’s structural support. The reduction of collagen and elastin fibres, combined with the loss of subcutaneous adipose tissue, results in a progressive sagging of the tissues. The skin is no longer able to effectively counter mechanical forces, which favours the appearance of pronounced folds and furrows.

Sleep-induced wrinkles.

The sleep wrinkles constitute a distinct category associated with repeated mechanical stress exerted on the skin during the night. Prolonged facial pressure against the pillow, night after night, can imprint transient folds which, over time, become permanent. These wrinkles are often vertical, asymmetrical and localised on the cheeks, neck or décolletage.

The various classifications outlined above can be cross-referenced with a more practical approach that categorises wrinkles by their location on the face. This provides an immediate insight into the areas affected by wrinkles.

Facial wrinkles do not arise from a single mechanism, but result from the complex interaction between intrinsic skin ageing, mechanical stress, muscle activity, and environmental factors. This explains the existence of several complementary classifications.

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