The Home Chemical Almanac · Chapter 6
Preservatives
Correct as of November 2026.
If the label says "preservatives"
Preservatives stop bacteria and mould growing in the bottle. Any water-based product, like laundry liquid, dishwashing liquid or a spray, needs some way to stay clean.
"Preservative" on a label is often one of the ten chemicals below. In Europe a detergent label must name them; here it often doesn't.
A word on contaminants: a few of these can carry or form unwanted by-products. In a well-made product the levels are low or nil, and that's the usual case. But you can't see it on the label, so it's worth knowing which ones carry the risk.
Cheat sheet
| Chemical | Badges | Also on labels as | Worst fact | Take care if |
|---|---|---|---|---|
| MIT | ☠ ⚠ | MI, methylisothiazolone | Allergy hit "epidemic proportions" in parts of Europe | eczema, MIT allergy |
| BIT | ⚠ | benzisothiazolinone | The rising allergy; not allowed as an EU cosmetic preservative | eczema |
| CMIT/MIT | ☠ ⚠ | MCI/MI, Kathon | Classed an allergen from just 0.0015% | MIT allergy |
| Phenoxyethanol | 🛢 💧 | — | Officially a US hazardous air pollutant | eyes |
| Sodium benzoate | 🛢 💧 | — | Can form benzene with vitamin C | chronic hives, asthma |
| Benzoic acid | 🛢 | — | EU: lung damage from repeated breathing in | handling the raw powder |
| Potassium sorbate | 🛢 💧 | — | One of the mildest: rare skin allergy | sorbic acid allergy |
| Bronopol | 💧 | 2-bromo-2-nitropropane-1,3-diol | Releases formaldehyde; Washington cosmetics ban 2027 | formaldehyde allergy |
| DMDM hydantoin | ⚠ 🛢 💧 | — | Built to release formaldehyde | formaldehyde allergy |
| Benzalkonium chloride | ☠ 🛢 💧 | BAC, BKC | Linked to asthma in cleaners and nurses | asthma, frequent eye drops |
☠ Poison schedule (Australia) · ⚠ Officially classed skin allergen · 🛢 Made from a hazardous chemical · 💧 Contaminant risk
The chemicals
- Methylisothiazolinone (MIT) ☠ ⚠
- Benzisothiazolinone (BIT) ⚠
- Methylchloroisothiazolinone / methylisothiazolinone (CMIT/MIT) ☠ ⚠
- Phenoxyethanol 🛢 💧
- Sodium benzoate 🛢 💧
- Benzoic acid 🛢
- Potassium sorbate 🛢 💧
- Bronopol 💧
- DMDM hydantoin ⚠ 🛢 💧
- Benzalkonium chloride ☠ 🛢 💧
Safer alternatives
The newer natural way to preserve a cleaning product is to keep it acidic. Citric acid and lactic acid lower the pH so most bacteria can't grow, and lactic acid is a registered antimicrobial in its own right, already sold as a preservative for household cleaners at a few percent.
Look for these on the label:
- Citric acid
- Lactic acid
Powders and other water-free products usually need little or no preservative.
Careful on stone: acidic cleaners can etch marble, limestone and travertine, so keep them off those (granite is more resistant). On engineered stone like Caesarstone, the maker says to use low-pH products with caution. Test a small spot first and rinse well.
Sources
Regulators and official lists
- Australian Government. Poisons Standard October 2026 (SUSMP), F2026L01327. Entries: methylisothiazolinone, methylchloroisothiazolinone, 2-phenoxyethanol, benzalkonium chloride. legislation.gov.au
- Safe Work Australia. Hazardous Chemical Information System (HCIS): classifications for each chemical and for benzene, ethylene oxide, toluene, phenol and benzyl chloride. hcis.safeworkaustralia.gov.au
- NICNAS (now AICIS). Isothiazolinones: Human health tier III assessment (2020); Methylchloroisothiazolinone IMAP assessment (2019); Bronopol IMAP assessment 1504 (2014). industrialchemicals.gov.au
- AICIS. Evaluation statement EVA00071: Quaternary ammonium compounds, alkylbenzyldimethyl, chloride (2022). industrialchemicals.gov.au
- European Commission. Cosmetics Regulation (EC) 1223/2009, Annex V; Regulations (EU) 2014/1003, 2016/1198, 2017/1224 and 2022/1181. eur-lex.europa.eu
- EU CLP Regulation (EC) 1272/2008, Annex VI harmonised classifications (incl. Reg (EU) 2018/1480). eur-lex.europa.eu
- Scientific Committee on Consumer Safety (SCCS). Opinions on methylisothiazolinone (SCCS/1557/15), benzisothiazolinone (SCCS/1482/12) and phenoxyethanol (SCCS/1575/16). health.ec.europa.eu
- European Medicines Agency. Questions and answers on benzalkonium chloride used as an excipient (EMA/CHMP/495737/2013, 2017). ema.europa.eu
- US EPA. Safer Chemical Ingredients List. epa.gov/saferchoice
- US FDA. Final rules on consumer antiseptic washes (81 FR 61106, 2016) and rubs (84 FR 14847, 2019); Q&A on benzene in soft drinks. fda.gov
- US CDC. Guideline for Disinfection and Sterilization in Healthcare Facilities: quaternary ammonium compounds. cdc.gov
- Washington State. WAC 173-339-110, formaldehyde releasers in cosmetics (from 1 January 2027). ecology.wa.gov
- European Food Safety Authority. Re-evaluation of benzoic acid and its salts (2016); sorbic acid and its salts (2019). efsa.europa.eu
- Japan NITE. GHS classification results for benzalkonium chloride (FY2017). chem-info.nite.go.jp
- US Cosmetic Ingredient Review. Final report on DMDM hydantoin (1988).
- Conseil d'État (France), decision No. 429578, 29 December 2022.
Studies
- Ljubojević Hadžavdić S et al. Methylisothiazolinone contact allergy in Croatia. Contact Dermatitis 2018;79:162-167.
- Lundov MD et al. Methylisothiazolinone contact allergy. Br J Dermatol 2011. doi:10.1111/j.1365-2133.2011.10523.x
- Søgaard et al. Benzisothiazolinone contact allergy, 2014-2023. Contact Dermatitis 2025. doi:10.1111/cod.14818
- Reeder MJ, Atwater AR. Cutis 2019;104:94-96.
- Purohit A et al. Occupational asthma from benzalkonium chloride. Int Arch Occup Environ Health 2000 (PMID 11007347).
- Quirce S, Barranco P. Cleaning agents and asthma. J Investig Allergol Clin Immunol 2010 (PMID 21313993).
- Santos, Li, Rustum. Impurities in benzalkonium chloride. Chromatographia 2010;71:499.
- Dendooven E et al. Sorbic acid and potassium sorbate allergy. Contact Dermatitis 2021 (PMID 33656744).
Acids and stone
- US FDA / Institute of Food Technologists. Evaluation and definition of potentially hazardous foods, ch. 3 (2001).
- US FDA. Bacteriological Analytical Manual, ch. 18: yeasts and moulds.
- US EPA. Product label 069132-00005, L-lactic acid in-container preservative (2023).
- Varvaresou A et al. Self-preserving cosmetics. Int J Cosmet Sci 2009.
- Natural Stone Institute. Care & Cleaning of Natural Stone.
- Caesarstone. Care and maintenance guide. caesarstone.ca