Mica

Mica is an inert mineral pigment/filler used in makeup and some skincare at low-to-moderate percentages; it is generally non-reactive on intact skin with very low rates of true allergy in patch testing. However, the plate-like particles can cause mild mechanical irritation or dryness in highly reactive or eczematous skin (and irritation can be more noticeable when applied repeatedly or over compromised barriers). For patient safety in severe sensitivity populations, it is best classified as very gentle rather than completely inert. Safety Notes: In commercial skincare and hybrid makeup-skincare (illuminating moisturizers, primers, sunscreens, body lotions), mica is often included at very low levels (~0.01–0.5%) to impart subtle sheen or improve slip, and can be present incidentally as part of a pre-dispersed pigment/pearl blend. At the high end, consumer-available loose highlighters, shimmer powders, and some pressed highlighters/finishing powders marketed as cosmetic/skincare-adjacent can contain mica as a dominant filler/pearlescent substrate, commonly 30–60% and observed up to ~70% depending on effect and whether other fillers/pigments are used. Levels are typically higher in leave-on color/finish products than in rinse-off products, where mica is usually used at low levels primarily for visual effect.