In an allergy, the body reacts to a substance that is in itself harmless. The human immune system — responsible for our defences — actually misjudges the situation and treats the substance as a pathogen, with a very strong reaction as a result.
An allergy or hypersensitivity to a particular substance usually shows up as a negative reaction in the airways/mucous membranes (think asthma and hay fever) or as a form of eczema. Eczema is an umbrella term for skin conditions where the skin is red and often flaky and itchy. Eczema can be dry (flaky) or wet (with blisters that may burst, releasing fluid). In a cosmetic allergy a cosmetic ingredient causes a form of eczema. The cosmetic ingredient is the trigger of a negative skin reaction and the eczema is the way that reaction shows itself. Allergy and eczema are therefore closely linked — particularly when an allergy involves cosmetic products.
How does an allergy / eczema develop?
Eczema can be congenital (also called atopic eczema or constitutional eczema) or it can be a reaction to yeasts on or in the skin (think of dandruff, for example). It can also be caused by contact with an irritating, aggressive substance (so-called irritant eczema, ortho-ergic eczema or non-allergic eczema, where the skin reacts almost immediately on contact with an aggressive substance such as turpentine), or by contact with a substance that triggers an allergic reaction.
This last form is typical of cosmetic-induced eczema and is also called allergic contact eczema or contact allergy. Such an allergy doesn't develop straight away — it builds up over time. The skin first has to be in regular contact with a substance for some time before the allergy actually develops. Sometimes that process can be completed within a few weeks, but it can also take years. Someone may tolerate a particular product well for years until they suddenly become allergic to it. An allergic reaction can be amplified by damaged skin (e.g. an "open leg" or someone with congenital eczema), by cold, friction, sweat, light (think of a sunscreen allergy that only appears once you're in sunlight), hay fever, or by another existing form of eczema. Once you have a contact allergy (allergic contact eczema), it's often for life.
The substance that triggers the allergic reaction is called an allergen. Not everyone reacts negatively to such an allergen. Only people whose immune system is sensitive to the allergen will have problems with that substance (whether or not a negative reaction occurs is determined by the way the immune system reacts to the substance in question).
Dermatological tests can be used to investigate whether allergic contact eczema is genuinely present and which allergenic substance is the culprit. Research by the RIVM (commissioned by the Dutch Food and Consumer Product Safety Authority) has shown that the most common allergy in consumer products (other than foods) is a nickel allergy. This allergy is generally caused by exposure to metal (clothing) accessories that contain nickel. The next most common allergy is to certain cosmetics (this can be make-up, but also hair dye, shampoo, deodorant, etc.). It's usually an allergy to fragrance (mix), Peru balsam or cobalt chloride (fragrance mix and Peru balsam are used in almost all cosmetics, including make-up; cobalt chloride is mainly used in hair dyes).
How do you recognise allergic contact eczema?
The most characteristic feature is that the eczema appears where the contact with the allergen has been. With a nickel allergy you therefore often see eczema around the navel (where the jeans button or belt buckle touches the skin), on the earlobe (where the earring sits) or under a watch strap. With a fragrance allergy you often see eczema behind the ears (where perfume is sprayed) or on the thin, vulnerable skin around the eyes (from a fragrance-containing eye cream, or because someone rubs their eyes with fingers that have nail polish on them). The skin in those places is then red, flaky and sometimes also has small blisters and/or bumps. The blisters may be filled with fluid and can even burst (with a risk of infection). In addition to these changes, the skin often itches as well. Contact eczema is not contagious.
Do you suspect you have an allergy?
When you have a negative skin reaction for the first time, it's tempting to draw a quick conclusion about what's causing the problem. However, it's advisable to investigate carefully what's actually causing the skin reaction. Often factors are at play that you don't initially think of. For example: watery eyes after applying make-up can be caused by the make-up. But they can also be caused by an applicator (which may contain latex), by nail polish on the nails (with the fingers touching the eyelids while applying eyeshadow) or by the make-up cleanser used to clean the face beforehand.
If you suspect you've had an allergic reaction to a cosmetic product, the following actions can be advisable:
• Doing a so-called "elbow-fold test" yourself. If you suspect you're reacting allergically to a particular product, you can carry out the elbow-fold test. This is only possible with products that stay on the skin for a long time, such as cream, body lotion or make-up (so this method can't test whether you're allergic to shampoo or bubble bath, since those products are rinsed off the skin). You apply the product to the inside of your elbow twice a day for 14 days. If you haven't had a negative skin reaction after two weeks, it generally means that you're not allergic to that product.
• Contacting your GP. The GP can issue a referral to, for example, a dermatologist (skin specialist). A dermatologist can use tests (with patch strips) to determine whether there's an allergy to a particular ingredient. If that turns out to be the case, the dermatologist can identify which ingredient is causing the allergy (often it's even multiple ingredients). The dermatologist can give the trade name of an ingredient as well as its "INCI name". To list cosmetic ingredients in a uniform way, it's a legal requirement that standardised names — known as INCI names — be used (INCI stands for "International Nomenclature Cosmetic Ingredients"). Once you know which INCI names you're allergic to, you can check the ingredients list (with INCI names) of any product. If the ingredient you're allergic to isn't on a product's list, you know that you can use that product safely without having an allergic reaction. Useful to know: INCI names are listed on every product in descending order of weight. When an ingredients list starts with, say, aqua, the largest component of the product is water. Ingredients present at less than 1% in the product may be listed in any order at the end of the ingredient declaration.
What do you do if you know you have an allergy?
If you know what you're allergic to, it's wise to avoid the ingredient in question. So it's important to look at every product carefully. The ingredients list (INCI) is essential here. For cosmetic products, manufacturers are required to display the INCI (on the product, or — if the product is too small — near the product, or for instance via the website associated with the product). Check this regularly, because over the years a manufacturer can change a product's composition, so a product can suddenly cause an allergic reaction (for example because a reformulated version is being used in which an ingredient you're allergic to has been added). So when buying a new product, always check the ingredient declaration, even if you've used the product for a long time without problems. The fact that a product is hypoallergenic, dermatologically tested, skin-friendly or pure-natural is never a guarantee here!
Depending on the severity of the allergic reaction, a doctor may prescribe a cream, apply a special dressing (particularly to prevent scratching of the skin), or possibly prescribe medication temporarily (prednisone) to settle the skin. In all cases, prevention is better than cure — carefully checking ingredients can prevent a lot of suffering!
Allergies and eczema have many forms and are extremely complex. With this article we provide general information based on research and general publications. We are not, however, medical experts.
If you suspect you have an allergy, we therefore strongly advise you to contact your doctor or a dermatologist for further personal advice.