The term "Hypoallergenic" essentially means makeup containing ingredients less likely to irritate the skin and is more of less a marketing tool- the FDA currently doesn't have any standards for "hypoallergenic" cosmetics or classify any makeup as hypoallergenic.
Link: http://www.fda.gov/cosmetics/cosmeticlabelinglabelclaims/labelclaimsandexpirationdating/ucm2005203.htm This of course doesn't mean you are not allergic or sensitive to ingredients. With that said, there are a multitude of things that can cause skin irritation: fragrance in makeup, ingredients used, contaminated products, etc. For clients that have this, I offer an assortment of gentle cosmetics that fall into the "Vegan product category" that are pro quality such as Urban Decay, Tarte, OCC, etc. The best thing would be to have a consult with a dermatologist, aesthetician, or allergist to pin point exact allergies to specific ingredients.
Thanks to Kate Jordan for her post on the subject which prompted me to write this entry.