Spermidine

Polyamine that boosts cellular autophagy and skin renewal.

Also known as: Spermidine trihydrochloride, N,N'-bis(3-aminopropyl)-1,4-butanediamine; same name in INCI.

What it is

Spermidine is a naturally occurring polyamine found in all living cells. It plays a key role in cellular metabolism, protein synthesis, and autophagy—the cell's "cleanup" process that removes damaged components and supports renewal.

What it does

Spermidine activates autophagy in skin cells, which enhances cellular turnover, reduces accumulation of damaged proteins, and supports collagen integrity. This mechanism may improve skin firmness, reduce fine lines, and promote a more youthful appearance. It also has mild antioxidant properties and may support skin barrier function.

The evidence

Emerging evidence supports spermidine's role in autophagy and longevity in cell and animal models; human skin studies are limited but show promise for improving skin elasticity and reducing wrinkle depth. The clinical evidence for topical use in humans is still developing.

Best for

Mature skin, loss of elasticity, fine lines, and those seeking cellular renewal and anti-aging benefits.

Pairs well with

Retinoids, vitamin C, niacinamide, and peptides—all support cellular renewal and collagen synthesis.

Use cautiously with

No major conflicts; generally well-tolerated alongside other actives.

Cautions

Well-tolerated at typical cosmetic concentrations; no known sun-sensitivity or pregnancy concerns, but data in pregnancy is limited—use cautiously or avoid if pregnant.