It is misleading to say a person is "allergic"; people are allergic to something specific, never to everything. When a substance causes an allergic reaction of the skin, the skin becomes very red where the allergen came into contact with it. This is accompanied by oozing and significant itching. If applications are repeated, reactions spread and the symptoms intensify. There are many different allergens (nickel, chromium, rubber, preservatives, fragrances, etc.).
In this case, there are very few visible signs on the skin: most of the time, patients experience tightness and burning that worsens each time a cosmetic product is applied, and these can become permanent and very uncomfortable. This is more common among women with thin, light and dry skin who are anxious and stressed. Patients say that they are "allergic to everything", but this is not an allergy, simply an excessive reaction of the skin that occurs in response to many products.
I first explain what is happening, as it is important to understand what is going on. In the case of actual allergies, you have to find the culprit allergen and stop using it. Patch tests are often necessary to prove the allergy. For reactive skin, I recommend gentle cleansers (preference for no-rinse cleansing lotions and thermal spring water spray mists) to avoid any irritating cosmetics. I recommend products that have been specially created for sensitive skin and that are formulated with anti-irritant agents.