Retinoid is the topical derivative of Vitamin A, which is found in butter and eggs and provides anti-aging skin benefits. Peter Thomas Roth Clinical Skin Care uses both Retinol and Retinoid in its products. Retinol Fusion PM Night Serum has a time-released, microencapsulated form of Vitamin A at 1.5% for minimal irritation while PRO Strength Retinoid Peptide Serum includes 10% Granactive Retinoid, an advanced type of Vitamin A that’s well-tolerated by most skin types with low potential for irritation, even at high concentrations. Each product is formulated for all concerns and helps improve the look of fine lines, wrinkles, uneven skin tone, texture and radiance. When using a topical Retinol or Retinoid, apply nightly with continued use and use SPF protection during the day. If mild irritation or redness occurs, use every other night until skin adjusts. Gradually build to nightly use.