Our Chief Medical Officer, Dr. Courtney Rubin, and our Head of Chemistry, Lizzy Trelstad, weigh in on your most pressing skincare questions.
Dr. Courtney Rubin’s take:
Almost any ingredient can cause irritation and allergy, but the most common causes of skin irritation and hypersensitivity reactions to beauty and personal care products are fragrances, preservatives, botanical extracts and/or essential oils.
Any ingredient can be irritating if used in excess. The dose makes the poison, as they say! However, the most likely ingredients to cause noticeable or immediate sensitivity are those that are volatile, such as denatured alcohol (alcohol denat. or SD-40).
Actives that are more likely to cause long-term sensitivity are ones that tend to be easily misused. These generally include vitamin A actives (retinol), mixtures of AHAs and BHAs and sometimes even vitamin C.
There's a laundry list of sensitizing ingredients, but I think it often comes down to someone's specific skin rather than one particular ingredient. Lots of ingredients on skincare “no” lists tend to be listed for a variety of reasons that are unrelated to skin sensitivity.