Spirulina

Overview

Spirulina is a dried biomass of Arthrospira platensis (still commonly labelled Spirulina platensis on cosmetic INCI), a spiral-shaped cyanobacterium. It grows in alkaline lakes and is cultivated commercially worldwide as a food, supplement, and cosmetic ingredient.

The cosmetic interest concentrates on three things: the deep blue-green colour (from phycocyanin, a unique water-soluble pigment-protein), the very high protein and amino acid content (~60% protein by dry weight), and the mineral and antioxidant load (iron, zinc, beta-carotene, vitamin E, chlorophyll).

The powder is intensely blue-green and gives a vivid colour to masks, body scrubs, and bath products even at low percentages. The scent is mildly seaweed-like, which fades in scented formulations.

Two cosmetic-grade products are common:

• Whole spirulina powder — the dried biomass, blue-green colour, mild scent, the standard ingredient.
• Phycocyanin extract — concentrated blue pigment-protein, used for vivid blue colouring in liquids and masks.

This entry covers the whole powder. Shelf life is 18-24 months stored cool, dark, and dry.

What it does in a formula

The main cosmetic effects come from:

• Phycocyanin — a unique antioxidant pigment-protein with research interest in anti-inflammatory and anti-aging skincare. Also responsible for the colour.
• Mineral load — iron, zinc, magnesium, and trace minerals contribute to “remineralising” claims, especially in masks.
• Amino acid content — high protein and amino acid load contributes to skin-conditioning and a mild film-forming effect.
• Carotenoids and chlorophyll — antioxidant contribution and a deeper green colour at high percentages.

In masks, spirulina pairs well with kaolin clay (for absorbent base) and honey or hyaluronic acid (for hydration and slip). The intense colour makes for a striking visual product.

How to use

Add to the powder phase of masks, scrubs, and bath products, or disperse into a water-based serum or gel with a thickener to keep the powder suspended.

Usage rates by product type:

• Clay face masks (powder): 2-10%
• Wet face masks and scrubs: 1-5%
• Bath bombs and bath salts: 1-5%
• Cold-process soap (colourant): 0.5-2%
• Body powders and dry shampoos: 1-5%
• “Green smoothie” style face serums: 0.5-2% (requires suspension)

For a clear serum or gel, use phycocyanin extract instead — the whole powder leaves visible green particles.

Best for / Worst for

Best for: clay masks (especially “detox” or “remineralising” positioning), bath products, brightly-coloured “ocean-inspired” cosmetics, body scrubs, hair masks, smoothie-style facial products with suspension.

Worst for: clear serums and toners (the powder settles and looks gritty), pale-cream formulations (the green tint dominates), customers with seafood or algae sensitivity (rare but reported), high-pH formulations (the phycocyanin colour shifts and degrades).

Common pitfalls

Smell. Spirulina has a distinct mildly fishy or seaweed-like scent that some customers find off-putting. Mask with essential oils (peppermint, eucalyptus, citrus) or use in heavily scented bath products.

Colour shift in soap. Spirulina in cold-process soap will often shift from vibrant blue-green to greener or duller olive over the first weeks of cure, as the phycocyanin reacts with the alkaline soap matrix. To minimise: use less spirulina, add at light trace, and accept the natural colour evolution.

Settling in low-viscosity formulas. Without a thickener, the powder settles within hours. Use xanthan gum or sclerotium gum for serum/gel formats.

Heavy-metal contamination. Spirulina is known to bioaccumulate heavy metals from its growing water. Always source from suppliers who publish lab tests for arsenic, lead, mercury, and cadmium. This matters for both cosmetic and food-grade product safety.

Confusing with chlorella. Both are micro-algae and both green, but chlorella is a different organism (Chlorella vulgaris) with a different chemistry — much lower phycocyanin (it doesn’t have the blue pigment), different protein profile, different uses. The two are not interchangeable.

Substitutes

• Chlorella powder — fellow green micro-algae, different chemistry, more chlorophyll-focused.
• Phycocyanin extract — concentrated blue pigment from spirulina, for vivid colour without the gritty powder.
• Green tea powder — fellow green botanical with antioxidants, no phycocyanin, more familiar.
• Matcha extract — concentrated green tea, also intensely green, more antioxidant load.
• Seaweed extract (existing entry) — water-based marine extract, no colour, different bioactive profile.