Almost all sunscreens contain inactive ingredients, or any other components of a product that do not affect the therapeutic action of the active ingredient. Some sunscreens contain an ingredient known as methylisothiazolinone. Methylisothiazolinone is a preservative and skin allergen which, according to the EWG, can lead to skin allergies and irritation. Even some products like baby’s sunscreen that are labeled hypoallergenic have methylisothiazolinone in them.
