If you are one of the many people who live with sensitive skin, makeup is something that should be used with consideration to limit any irritation.
Beauty products are complex and have a wide array of ingredients that all serve a purpose. It is not uncommon for mass produced cosmetics to be loaded with fillers and preservatives to make it more cost effective to produce and to be kept on the shelves of the stores for extended periods of time. With an abundance of potential irritants, if you are using several products at a time, your skin already has too much to deal with. Natural cosmetics as a rule have much less within them and will not overload your skin in the same way. As an example, our powdered mineral foundation has a mere 6 ingredients whereas many companies will have at least twice that within a similar product.
If your makeup has been sitting around for a long time, there is also bacteria that can accumulate. If it is past its expiration then there will be decay which can cause a further reaction on your skin. If you were to take that same product and apply it to your face with a tool that has not been cleaned properly, there are additional microbes to consider. Makeup should also always be stored in such a way that it is kept sealed, cool and dry to keep this to a minimum.