Common Name(s): Ammonia solution,nh4oh,household ammonia

CAS Number: 1336-21-6

DESCRIPTION

What It Does: Opens hair cuticle for dye penetration and activates hydrogen peroxide at alkaline ph.

Why It's Used: The hair colour alkaliser – ammonium hydroxide's rapid cuticle-swelling and h2o2 activation makes it the most effective and fastest permanent hair colour alkaliser.

How It Works: Nh3 (volatile base) alkalises hair colour to ph 9-11. at alkaline ph, hair keratin proteins become ionised and water-swollen, allowing dye molecule penetration through swollen cuticle into cortex. high ph activates h2o2 for melanin bleaching. volatile nh3 evaporates during processing.

Typically Found In: Permanent hair colour formulations

TECHNICAL DETAILS

Primary Category: Hair colourant – alkalising agent

Secondary Functions: Skin conditioning

Application Areas:

Typical Concentration Range: 0.5%–6%

SOURCING & ETHICS

Vegan Status: Conditional - supplier confirmation required

Halal Status: Unverified - supplier confirmation required

Source Notes: Commercially produced for cosmetic use. verify vegan/halal status with supplier. [audit 2026-07-29 rev2: the record's own source_notes does not assert a non-animal origin, or instructs the reader to verify with the supplier; "yes" asserts knowledge the record does not hold. determination requires shariah-panel sign-off.]

SKIN COMPATIBILITY

Irritancy Rating: 1/5 – very low

Comedogenicity Rating: 0/5 – non-comedogenic

Sensitivity Concerns: Well-tolerated by most skin types.

Safe for Sensitive Skin: Yes

SAFETY & COMPATIBILITY

Safety Profile: Eu annex iii restricted: max 3.5% (in hair colour) or max 6% (other hair products). scalp irritant at high concentrations. strong odour. sensitiser to some.

Works Well With: Standard skincare actives

Avoid Combining With: No known significant incompatibilities

SCIENTIFIC NOTE

Ammonium hydroxide's volatile nh3 provides a unique self-limiting alkalinity system: as the hair colour processes, nh3 evaporates from the alkaline emulsion, gradually reducing ph back toward neutral. this self-limiting ph reduction prevents excessive prolonged alkaline damage to hair protein structure – an elegant chemical safety mechanism built into the volatile base system that would not occur with non-volatile alkalisers.

Last Verified: 2026-03-12

Primary Sources: Cosing database,eu annex iii,cir safety assessment