Dr. LanAnh Do-Tarnay says: Unless you know the specific ingredient you are allergic to, it would be difficult to know if you are allergic or sensitive to a makeup or skincare product until you try it. Reactions can include rash, redness, itch, swelling, and dryness. Those with sensitive skin should consult an allergist or dermatologist to help identify their allergen, perhaps through testing, so they can avoid products with those ingredients in the labeling. Otherwise if you have sensitive skin and are not certain of your allergen, when trying a new product, apply a small amount to your neck, wrist, or flexor part of forearm first and leave it on for 24hrs or apply for up to a week to see if there is a reaction.

Dr. LanAnh Do-Tarnay says: “Hypoallergenic” implies that something is less likely to cause an allergic reaction. So, a hypoallergenic product infers that it does not have or it contains fewer ingredients known to be allergenic, and therefore less likely to trigger unwanted adverse skin reactions.
New allergens emerge with time and the list of top allergens get updated. So for those with sensitive skin, you’d want to select a hypoallergenic product from a trusted brand committed to monitoring the changing top allergenic ingredients lists and formulating their products to reflect the change.