Allergic Contact Dermatitis results when an allergen (something that causes Allergy) comes into contact with skin. The most common causes in US are nickel in Mascara and eye shadows, balsam of Peru in Perfumes, Deodorants, Aftershave, and oak in cosmetic products.
Regarding possible allergens in cosmetics, the best way to prevent an Allergy is to know what you are sensitive to and how to avoid it. One way to accomplish this is by carefully reading the product ingredient panel and avoiding ingredients you know or think you are allergic to. It isn’t enough to check for terms like “hypoallergenic”, “fragrance-free” or “for sensitive skin”.
There is some good new, Folks! You don’t have to wait until you have an allergic reaction to try and figure out what you are allergic to. Knowing precisely what allergen has caused a reaction will help you to avoid further exposure to the substance.
Your healthcare provider may recommend you undergo patch testing or some other, less frequently used tests.
Different Tests to Know if You Have Allergy
Patch Test
It consists of application of substances suspected to be the cause of the dermatitis to intact uninflamed skin. Patch testing use thin-layer rapid-use epicutaneous (TRUE) test or individual patches. Apply test substances to the upper back, although, you can also use the upper outer arm for fewer number of patches.
Number each patch to avoid confusion. The patches are removed after 48 hours (or sooner if severe itching or burning occurs at the site) and read. The patch sites need to be evaluated again at day 4 or 5 because positive reactions may not appear earlier. Some allergens may take up to day 7 to show a reaction. Irritated skin at the patch site may indicate an allergy.
Provocative Use Test
Rub the products that stay on the skin for long periods (ex. Make-ups) on normal skin of the inner aspect of the forearm several times daily for 5 days. A pink itchy patch will indicate the need to avoid the product.
Photopatch Test
The photopatch test evaluate contact photoallergy to substances like sulfonamides, phenothiazines and p-aminobenzoic acid. Apply a standard patch test for 48 hours, expose to UVA then read after another 48 hours. There is an increasing incidence of photoallergy to sunscreen agents and a decreasing incidence of such reactions to fragrance.
READ MORE!
https://skincaretopnews.com/difference-between-dehydrated-and-dry-skin/
 comes into contact with skin. ...Mascara and eye shadows...){kind=link}