Chapter 5: Enzymes
Protease
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The worst fact: at five UK detergent factories, 166 cases of asthma thought to be caused by enzymes were recorded over 20 years, 140 of them between 1968 and 1974, when airborne enzyme levels were highest. In the most exposed group, 38% (233 of 619 workers) tested positive for enzyme allergy on skin-prick tests. Australia classes it as "Causes serious eye damage", "Causes skin irritation", "May cause respiratory irritation" and "May cause allergy or asthma symptoms or breathing difficulties if inhaled".
Why brands use it: it breaks down protein stains such as blood, egg, milk, meat and grass.
Take care if: you have asthma or allergies. Spray stain removers with enzymes release the most airborne enzyme of any household task in industry measurements, so spray away from your face. Rinse your hands after using a stain pre-treatment, which can mildly irritate skin. For factory workers, Australia's limit (from 1 December 2026) is a peak of 60 nanograms of pure enzyme per cubic metre of air, which must not be exceeded at any time. Industry measurements of household laundry tasks range from almost nothing to about 3 nanograms per cubic metre (spray pre-treaters about 14.5), well under that limit.
Comes from: fermentation by Bacillus bacteria, now mostly genetically modified strains. Some detergent proteases, increasingly, are also protein-engineered to survive bleach.
Myth check: "Enzymes eat your skin": no. The molecules are too big to get through healthy, unbroken skin, and wash water is far below the level that irritates.
Contaminants: nil. Enzyme preparations also carry small amounts of other enzymes, salts and fillers from manufacturing; these are part of the ingredient, not contaminants.
Fair to say: in 1971, a US National Academy of Sciences committee, relying on letters from consumers and doctors, found only six clear cases of consumers becoming allergic to enzymes, at a time when about 50 million American homes used the old dusty powders. A Swedish study from that era found enzyme antibodies in 15 of 1,645 people (0.91%). Since the early 1970s, detergent enzymes have been added as coated, dust-free granules. A 2010 review by detergent-maker scientists of 15,765 people found enzyme antibodies in 0.126% of those tested after 1977, with no symptoms linked to laundry products. It breaks down readily, and over 99% is removed in sewage plants.
Correct as of November 2026. What the badges mean
Sources
- Safe Work Australia. Hazardous Chemical Information System (HCIS): subtilisin, alpha-amylase, cellulase, mannanase.
- Safe Work Australia. Workplace exposure limits for airborne contaminants (amended November 2026): subtilisins.
- HERA. Subtilisins (protease), 2nd ed. (2007); alpha-amylases, cellulases and lipases (2005).
- Cullinan P et al. An outbreak of asthma in a modern detergent factory. Lancet 2000;356:1899-1900.
The full source list is at the end of Chapter 5.