Each person is unique, and so are the substances that trigger allergies. An allergic reaction happens when your immune system reacts to a foreign substance that it believes is dangerous. This means more than just makeup -- allergic reactions can be triggered by many things from certain foods to pollen, and they can develop over the course of your lifetime, meaning that something you once were not allergic to could become a sudden problem. There is no cure for allergies, but there are steps you can take to improve your situation, especially when it involves makeup [source: Mayo Clinic].
Most adults use seven or more skin-care products every day, ranging from makeup and facial cleanser to body soap and deodorant [source: American Academy of Dermatology]. Just one ingredient in one of those products can be linked to an allergy or skin irritation. Studies have found that up to 10 percent of the population will have a reaction to a cosmetic product during their lifetime [source: MedicineNet].
The ingredients that are most likely to set off an allergic reaction are fragrances, which are found in most skin-care products. If you find that your skin is irritated by scented products, keep a watchful eye on the "unscented" products too, which can mean a product might still contain a fragrance. Here, the fragrance isn't enhancing the scent of the product; it's merely masking the smell of the chemicals it contains. Look for "fragrance free" or "without perfume" to know that the cosmetic you are buying truly hasn't had a fragrance added to it [source: American Academy of Dermatology].
Preservatives are another common allergen found in makeup. The culprits often have long, difficult-to-pronounce names such as phenoxyethanol or imidazolidinyl urea. And if you're not sure whether something in your makeup bag contains a preservative or not, a general rule is any cosmetic product that contains water must also contain a preservative [source: American Academy of Dermatology].
While red, itchy rashes are common symptoms of makeup allergies, there are other telltale signs that your skin's reacting poorly to your makeup.