The common adverse effects in cosmetics.

In the form of a gel, balm, cream, oil, or soap, a cosmetic product is designed to be applied to a specific part of the body, most often to cleanse or enhance it. However, the use of cosmetics can also lead to adverse effects, manifesting as a allergic reaction or irritation. The onset of these symptoms is caused by the presence in the product's formulation of one or more ingredients that the skin cannot tolerate. It should be noted that skin tolerance varies from one person to another: a product causing adverse effects in one person may be completely harmless to another.

The prevention of adverse effects is achieved through a test systematically carried out on products before the first application and strict adherence to usage instructions.

A skin irritation.

One of the most common adverse effects in cosmetics is skin irritation. Most often, it manifests immediately after the application of the product and is characterised by itching and tingling sensations. Irritation can also lead to widespread redness and skin dryness. More common in sensitive skin, these symptoms often occur when frequently using or applying large amounts of products concentrated in retinoids or AHA (glycolic acid, mandelic acid...) or containing fragrances or sulphated surfactants, such as sodium lauryl sulphate. The irritative reaction compromises the skin barrier and reduces its water retention capacity, leading to dryness and flaking.

How to respond after a skin irritation? When the skin is irritated, it is advisable to scale back your skincare routine and use moisturising and soothing products in the following days, in order to reduce inflammation, rehydrate the skin and promote its quick recovery.

An allergic reaction.

Unlike a simple skin irritation, an allergic reaction to a cosmetic product takes several days to manifest. Often presenting as hives, swelling and blisters, the allergy is caused by the presence of one or more allergens (such as fragrances, essential oils...) that the skin cannot tolerate. Biologically, when an allergen penetrates the skin, the immune system recognises it as a threat. Lymphocytes, which are immune cells, are then mobilised to release inflammatory mediators like histamine, causing the characteristic symptoms of an allergy.

What to do after an allergic reaction? Effective management of an allergic reaction involves completely avoiding the responsible cosmetic product. In the following days, the topical application of a soothing cream and/or one containing corticosteroids can also help to reduce inflammation and itching.

Cosmetic acne.

Another recurring adverse effect after using a new cosmetic product is the emergence of spots, which can take the form of whiteheads, blackheads, papules or even pustules. These spots are often due to a skin purge, a phenomenon characterised by an acceleration of cell renewal that causes a rapid surface appearance of imperfections. Several active ingredients, such as retinol or glycolic acid, are likely to trigger a purge. However, if the product causing your spots contains no exfoliating agents, it may be comedogenic for your skin. These are generally products with a rich texture, containing occlusive ingredients capable of blocking the skin's pores and preventing the evacuation of sebum, such as coconut oil or certain waxes.

How should you react if a product causes spots? If the product is comedogenic for your skin, it is advisable to stop using it. The spots will then disappear spontaneously within a few days. In the case of a purge, we recommend you to continue using the product. This inconvenience is indeed temporary and allows all imperfections to be expelled at once, resulting in clear skin afterwards. Several factors can help identify a purge.

An ocular irritation.

Extremely delicate, the eyes are also affected by the adverse effects of cosmetics. An ocular irritation is most often manifested by symptoms such as redness, itching, tearing, a burning sensation and sometimes swelling of the eyelids. It is generally caused by the application of eye makeup, such as mascara, eyeshadow or concealer, containing irritating or allergenic ingredients. Cases of misuse are also common around the eye contour. That's why it's important to check the usage instructions before applying a product to this sensitive area.

What to do in case of eye irritation? If your eyes are irritated, it is recommended to gently rinse them with warm water to remove any cosmetic residue, avoiding rubbing them. Subsequently, it would be advisable to avoid reusing the product in question. If the tingling and dryness persist in the following days, the use of soothing eye drops, available at pharmacies, may provide relief.

A photosensitivity.

Some cosmetic actives are only used in the evening and require the application of sun protection the following morning. These molecules, known as photosensitisers, are capable of increasing the skin's susceptibility to sunlight and causing exacerbated sunburn. Biologically, photosensitising actives cause molecular changes in the skin, making it more sensitive to UV rays.

How to deal with photosensitivity? If you are using photosensitising actives in your skincare routine, it is crucial not to forget to apply daily and in sufficient quantity a sun protection. If your skin still develops a sunburn, use hydrating and nourishing actives such as ceramides or vitamin B12 to restore the skin barrier. In case of blisters or intense pain, consult a healthcare professional to receive appropriate treatment.

A change in pigmentation.

Less commonly, certain cosmetics can lead to pigmentation irregularities, manifesting as brown spots or discoloured areas. Indeed, substances such as retinol or AHAs and certain lightening agents like kojic acid can influence the production of melanin by the skin's melanocytes. An acceleration of cellular renewal can particularly lead to a loss of pigmentation due to a rapid maturation and differentiation of epidermal cells. Unwanted pigmentation changes linked to the use of a cosmetic are generally temporary.

What to do in case of pigmentation changes? If you notice changes in your skin colour, it is essential to immediately stop using the products responsible. Return to a minimalist routine and ensure you apply a broad-spectrum sunscreen with a high SPF every day of the year to protect the skin from UV rays, which can exacerbate pigmentation irregularities. If these persist, it is recommended to consult a dermatologist so they can provide advice and appropriate treatment.

Good to know : The European regulation incorporates a system of cosmetovigilance with the aim of cataloguing the adverse effects caused by cosmetics and improving consumer safety.