Nickel is a mineral, derived from limotite, granirite and pendalite (three mineral types of which the last only occurs in magma that comes to the surface in volcanic explosions). In the list of ingredients, Nickel is indicated as NI. Nickel is common in food and in stainless steel. Regularly wearing piercings, earrings and belts with metal buckles can cause an allergy to nickel. This manifests itself in a rash that itches and may produce watery blisters. Nickel allergy sufferers are generally more likely to have an allergy to, or skin irritation with, many other ingredients such as cobalt, copper, zinc, water, soap suds, etc.

Nickel is hardly used in make-up. The make-up products of Unity Cosmetics do not contain nickel.

Nickel is often confused with iron oxide. Iron oxide gives colour to a product and is used by almost all cosmetic brands (including Unity Cosmetics). Iron oxide (in the inci list recognizable as CI77499, 77491, 77492 and 77489) comes from a natural mineral called "hematite". Bringing hematite into contact with oxygen creates iron oxide, which is therefore often used as a pigment in cosmetics (it is also regularly found in food). Iron oxide is a frequently used and safe ingredient for which, contrary to nickel, one seldom or never builds up an allergy. 

Iron oxide is used in most products of Unity Cosmetics because it is a mineral that gives beautiful colours and generally does not cause negative skin reactions.