murphyCalcium Hydroxide
AKA: 1305-62-0, Slaked lime, Hydrated lime, Lime hydrate, Calcium hydrate, Lime water, Calcium hydroxide (Ca(OH)2), Hydralime, Slaked-lime
Synthetic
Not Clean
OriginCalcium hydroxide is produced from limestone (calcium carbonate) through thermal decomposition or slaking of quicklime. It is synthesized by heating calcium carbonate to create calcium oxide, then adding water in a controlled hydration reaction.
The CIR Expert Panel concluded that ... Calcium Hydroxide is safe in hair straighteners and depilatories under conditions of recommended use; users should minimize skin contact. These ingredients are safe for all other present practices of use and concentration described in this safety assessment when formulated to be nonirritating.
Solubility 0.2 % at 32 °F (NIOSH, 2024)
Formula
CaH2O2
Mol. Weight
74.09
CAS #
1305-62-0
Form
Powder
State
Calcium hydroxide is an odorless white granules. Sinks in water. (USCG, 1999)
Skin Types
●all-skin-types
Best For
General
Pregnancy & Breastfeeding Safe
Yes
Functions
Buffering
Antioxidant
Anti-Inflammatory
Boosts Collagen
Maintains optimal pH
The paper trail
🔬Peer-reviewed1 paper →
⚖️Regulatory1 listing →
🛡️Safety-assessed2 reviews →
Counts, not a verdict. A listing isn't a study. The trail, you decide.
EWG
4
CIR
Safe as used
Pregnancy
Yes
CIR Safety Findings
Skin Irritant in Testing
1 study / 1 irritating (CIR 703)
Eye Irritant in Testing
2 studies / 2 irritating / reactions severe (CIR 703)
Concentration Guide
Leave-on0.11–0.5%
Rinse-off0.1–13.2%
0%50%100%
Reg. limit 7%
CIR reported use · report published 2021
EU regulatory limit: 7%. (a) Contains alkali Avoid contact with eyes Keep out of reach of children Can cause blindness (b) Contains alkali Keep out of reach of children Avoid contact with eyes Source: EU Cosmetics Regulation (EC) 1223/2009, Annex III (Restricted Substances), Entry 15c.
Regulatory Agencies
Verified Jun 2026
Data: PubChem · CosIng · EWG · CIR