Sensitive skin is typically understood as skin that is prone to irritation and itching when using common toiletries and cosmetics. According to a 2006 review article in Contact Dermatitis, 50% of women and 38% of men say they have sensitive skin. Excess dryness or oiliness, stinging sensations and the like can all be parts of sensitive skin.
The barrier designed to keep out irritating substances can be weakened by age, heat, air conditioning, cold weather, harsh chemicals, the sun, big changes in pH and more. When the barrier is weakened, the skin will respond with redness, stinging, blotches, tightness or breakouts.