Summarize:

In medical studies, nearly half of the population has been shown to have characteristics of sensitive skin.  These include redness and/or abnormal stinging, tingling, or burning sensations that occur in response to certain triggers (which can vary from person to person). If you have very sensitive skin with redness and bumps, particularly if you are a woman over 20, you may have a common skin condition called rosacea. This skin condition is also common in people who have had acne. There are several subtypes of rosacea, so it’s best to see a dermatologist if your skin is very sensitive and prone to redness. Triggers are highly variable between people, and it takes experience to find out what causes your skin to become irritated (it will be different for each person). Triggers may include:  particular weather (such as sun, heat, wind, and/or cold) certain cosmetics certain soaps stress your menstrual cycle (for females), although this one cannot be avoided. Using the wrong products can worsen your sensitive skin, so it is best to get a handle on what works for you before attempting to add acne treatments. Avoid products that contain alcohol, menthol, or “exfoliating” agents. These can irritate skin and make acne worse.  In general, using fewer products on your skin is better. Look for products that are labeled "hypoallergenic" at the drug store or pharmacy. Or, ones with fewer ingredients (and more natural ingredients) tend to be a better bet. Always observe the response of your skin to various cosmetics and soaps. Go by trial and error and eliminate those that cause you trouble.
Understand that sensitive skin is very common. Identify what triggers your sensitive skin, and avoid these whenever whenever possible. Select appropriate cosmetics and skin care agents for your skin.