Many patients complain of sensitive skin and attribute them to skin care products. Sensitive skin can often be confused with allergic skin. It is important to distinguish the two. Sensitive skin is seen in patients with common skin conditions like rosacea. Allergic skin reactions occur when allergens and other chemicals in skin care products penetrate a weakened skin barrier and invade the deeper layers of skin. Unfortunately, the list of preservatives and fragrances to watch out for is long. A dermatologist can expertly diagnose what you're allergic to by using a personalized patch test where many potential allergens are taped to a patient's back; when the tape is removed 24 to 48 hours later, corresponding allergies can be identified.