Skittles are a small, brightly colored confectionery composed primarily from sugar and oil. They are advertised as "fruit flavored" but contain both natural and artificial ingredients. There are many different variates of Skittles. The most common is Skittles Original, which were originally a European candy until imported to the United States in 1979.
From the Marshealthyliving.com website:
Skittles Original contain sugar, corn syrup, hydrogenated palm kernel oil, apple juice from concentrate; less than 2% - citric acid, dextrin, modified corn starch, natural and artificial flavors, coloring (includes yellow 6 lake, red 40 lake, yellow 5 lake, blue 2 lake, yellow 5, red 40, yellow 6, blue 1 lake, blue 1), ascorbic acid (vitamin C)
Because ingredient lists are usually in order of percentage, we can deduce that the major ingredient in Skittles is sugar, followed by corn syrup and hydrogenate palm kernel oil. The other ingredients are mainly flavors and coloring, which add a tiny amount of nutrition.
To many, the worrying ingredient on this list is the Hydrogenate Palm Kernal Oil. Hydrogenation is a process used to keep oils from liquefying, and is a source of saturated and trans fats, which are considered unhealthy in large quantities. The website also lists 2 grams of fat per serving, all of which is saturated fat; this lists as 10% of a daily requirement. Overall, Skittles are a low-fat candy, but should be consumed in moderation.