Why do we have sensitive skin?

Sensitive skin is a skin condition. It can therefore affect people with dry, combination or oily skin. However, it should be noted that dry skin types are generally more prone to skin sensitivity. This can be explained by their lower sebum production and the more limited effectiveness of their hydrolipidic film. This skin type is thus less protected against external aggressions. The main manifestations of sensitive skin are as follows: tingling, tightness, sensations of heat, redness, irritations, but also acne outbreaks or inflammations

From a biochemical perspective, according to recent studies, the level of corneocytes is reduced in individuals with sensitive skin. These molecules constitute the stratum corneum, located on the surface of the epidermis, and play a protective barrier role. A stratum corneum with fewer corneocytes results in weaker protection and more effective transcutaneous penetration of chemicals.

Furthermore, in sensitive skin, there is a higher presence of pro-inflammatory cytokines, proteins that are partly responsible for the redness and inflammation frequently observed in reactive skin. It is also observed that the synthesis of filaggrin, a protein in the epidermis playing a key role in the skin barrier, is less significant in individuals with sensitive skin. Lastly, it has been demonstrated that the expression of certain transglutaminases, which also contribute to the skin's barrier function, is weaker in sensitive skin.

Several factors can be responsible for skin hypersensitivity, among which include:

• Heredity.

  Some individuals have had sensitive skin since birth. Genetics can be responsible for this condition, with fair-skinned individuals naturally inheriting a more reactive skin type. Those possessing this phototype generally have a lower quantity of skin pigments and a thinner epidermis. It is also possible that a mutation on the gene coding for the filaggrin protein could be responsible for certain skin hypersensitivities.

• Hormonal fluctuations.

  Skin sensitivity can also develop over time. Stress can sometimes be responsible. This leads to an increase in the level of cortisol in the blood. This hormone contributes, among other things, to the breakdown of collagen, a molecule that makes up the extracellular matrix and helps maintain the structure of the skin barrier.

• The dietary regime.

  Diet can also play a role in skin comfort. Certain foods, known as stimulants, such as coffee and chilli, can slightly increase body temperature. This increase promotes the dilation of blood vessels, which tends to be more noticeable on sensitive skin. Similarly, a high consumption of saturated fats has pro-inflammatory effects, and can exacerbate skin sensitivity.

• The intake of medication.

  Corticosteroids , whether taken orally or used topically, can induce a skin rash resembling acne. Certain anti-inflammatory drugs can also cause photosensitisation of the skin. That's why it is recommended for sensitive skin to apply a broad-spectrum sunscreen before each exposure.

• Sudden variations in temperature.

  Due to the dry cold, the secretion of sebum decreases, which leads toskin dehydration. The hydrolipidic film that protects the skin becomes thinner and as a result, the skin is less protected. Simultaneously, the desquamation, or the process of skin renewal, is disrupted, which can lead to the appearance of redness and irritations on the skin.

• The use of unsuitable skincare products.

  Some active ingredients, such as essential oils, sulfates, and fragrances, are poorly tolerated by sensitive skin and can cause undesirable, even painful reactions. Indeed, essential oils contain several allergens such as linalool and limonene. Sulfates, often found in shampoos or shower gels, are likely to damage the hydrolipidic barrier by clinging to the lipids of the stratum corneum. Finally, fragrances contain several alcohols, potentially irritating or allergenic.

  The use of grain scrubs, or mechanical ones, which require significant rubbing, can also exacerbate skin sensitivity. When one has sensitive skin, it is better to turn to enzymatic or chemical scrubs, which are gentler.

• Hard water.

  After a shower with hard water, feelings of skin tightness can occur, accompanied by various issues such as irritations, itching, and even the appearance of red patches. The explanation is as follows: the calcium and magnesium ions, which make up hard water, form microcrystals on the skin, causing the prickling sensations.

• MAIBACH H. & al. Sensitive skin: an overview. International Journal of Cosmetic Science (2012).

• LANE M. & al. A fundamental investigation into aspects of the physiology and biochemistry of the stratum corneum in subjects with sensitive skin. International Journal of Cosmetic Science (2016).

• STANDER S. & al. Sensitive skin. Journal of the European Academy of Dermatology and Venereology (2016).