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While both are powerhouse ingredients, they work best at different times. Vitamin C is an antioxidant that protects against environmental stressors during the day, so it should be used in the morning.

Retinol is light-sensitive and aids in repair, making it ideal for nighttime use.

Both are highly active ingredients. Using them together in one step can lead to significant dryness, redness, and peeling, especially for sensitive skin.

Peptides are short chains of amino acids that serve as the building blocks of proteins like collagen, elastin, and keratin. In skincare, they act as cellular messengers. When collagen breaks down, it creates peptides that signal the skin to “repair” itself by producing new collagen. Applying topical peptides tricks the skin into thinking it needs to generate more structural proteins.

Do they actually penetrate the skin? Historically, peptides were considered too large to bypass the the skin’s outermost protective layer. However, modern cosmetic chemistry has solved this in two ways:

1. Lipid tails: Scientists now attach fatty acid chains (like Palmitoyl) to peptides, making them lipophilic so they can slip through the skin’s oils.

2. Molecular weight: Modern lab-synthesized peptides are engineered to be small enough to reach the deeper layers where fibroblasts (collagen-producing cells) live. So, it is not just marketing, but the formula’s delivery system matters as much as the peptide itself.

E.g. signal peptides (e.g., Matrixyl 3000 / Palmitoyl Pentapeptide-4) are the most popular. They tell the skin to boost collagen and elastin production to firm the face and reduce wrinkles.

Most dermatologists recommend starting Retinol in your early 30s. It is a derivative of Vitamin A that accelerates cell turnover and boosts collagen production. Its meant to reduce the appearance of fine lines, improving skin texture, and fading hyperpigmentation caused by sun damage.