Nappy Leaks: Bio Hazard?

What we have learned so far about biological laundry detergent.

Welcome to the inaugural post in Nappy Leaks, the slightly lighter side of the Nappy Science Gang blog. Here, some NSG citizen scientists (both expert and downright amateur) will be squishing their fully loaded brains and letting the results dribble right down your screen. Stay tuned for a steady peristalsis of brain dumps. Today, it’s all about biological washing powder.

Not long ago Nappy Science Gang celebrated a victory for citizen science when the mighty NHS changed its guidelines on the use of biological washing powder in response to our work (read more here). It caused a bit of a stir because what we found looking at evidence, and what the NHS acknowledged having looked at the evidence, contradicts what has been a ‘truth’ of the reusable nappy community for a long time, that biological washing powder is bad, m’kay?

Lots of you still have questions, so here is a round-up of what we’ve learned from science and industry experts about biological washing powder so far, starting with the two big issues of whether it’s harmful to skin and whether it’s harmful to reusable nappies.

Does biological washing powder cause skin irritation?

In short, no. “Biological” means containing enzymes, special digestive compounds borrowed from microorganisms which eat away certain substances. In a laundry detergent they attack some substances which soil clothes and some tiny loose fibres of the cloth, but they rinse away and they don’t attack skin. In several tests it’s been shown that detergents containing enzymes caused no more irritation than those which didn’t, even after prolonged contact with skin. At least one enzyme is a known allergen if you inhale it in its raw form but, in laundry detergent, it’s encapsulated in little beads so that that doesn’t happen. You can read about the evidence here.

Do biological enzymes degrade my nappies?

The answer is yes, though only a little over the lifetime of using and washing the nappies. Washing is the biggest wear factor on any nappy. All cleaning wears clothes. To get your clothes clean your washing machine creates agitation by tumbling the load to rub your clothes together, replacing the action of scrubbing on a washboard or bashing against stones in a stream. Over time this causes wear. The chemical actions of the various cleaning ingredients in your washing powder also cause wear and enzymes are only one of many such ingredients. So cleaning degrades your nappies and the effect of enzymes is only a small part of that effect.

Different detergents use different combinations of enzymes. Here are some of the big names:

  • Lipase, which acts on oily substances. This is big contributor if you want to use less surfactant, one of the reasons enzymes are considered a good choice for the environment.
  • Amylase, which acts on starches. Perhaps this the thing that can dissolve Weetabix?
  • Cellulase, which acts on cellulose. As well as attacking stains, this one can even help keep your clothes looking newer.
  • Protease, which acts on proteins. It’s good for food stains, blood and ‘body soils’, so cleaner collars and cuffs, and hopefully knickers you can get run over by a car in.

Enzyme developers fine tune these to particular aptitudes like operating at low temperatures or in a short wash, and they are developing new enzyme products all the time. Pectate lyase might be used to seek and destroy fruit stains, and mannanase’s nemesis is the gums that are found in lots of processed foods these days.

But what about cellulase? I’ve heard it eats nappies alive!

Cellulase breaks down tiny protruding fibres of cellulose, an organic compound which is a major component of natural fibres like cotton, ‘bamboo’ (viscose from bamboo), and hemp. Why on earth would you want your detergent to digest the very stuff your nappies are made of? When they are washed, those natural fibres get damaged and develop microscopic bristly patches which trap particles of dirt. Cellulase can snip off the tiny bristles. By snipping them off you both clean that dirt away and smooth the bristly patch so the dirt can’t easily attach there again (more info here, on page 17).

So are biological enzymes just for removing stains, rather than actually cleaning?

No. They also help to break down proteins, fats, starches and more which form part of wee and poo. Because they help to break down dirt in your nappies and remove it from the cloth, they also help get rid of bugs by destroying their food source and habitat and allowing them to be washed away. UPDATE 11/05/16: In our chat with medical microbiologist Clare Taylor we learned that poo is mostly made of bacteria and that bacteria themselves are made of proteins, sugars and fats, so bio enzymes should be very useful for attacking them in the wash.

I’m not sure I believe you about it being safe on skin: I’m definitely allergic to biological powder.

Research has shown repeatedly that products with enzymes don’t irritate any more than those without. Enzymes are encapsulated in detergent powder and they should also rinse away once they’ve done their job. However there are lots of other ingredients in both bio and non-bio laundry detergent which could be causing irritation. For example, fragrances and optical brighteners are designed to stay behind in the fabric and have been known to cause reactions. Detergent manufacturers don’t tell us the ingredients or how they differ but most offer both a bio and a non-bio formulation with the non-bio version targeted at the sensitive skin market. That appears to be a red herring because in other parts of Europe non-bio is hardly sold, however biological formulations which are fragrance free are available for those with sensitive skin. In the UK you might find that a brand only offers a ‘sensitive’ package with fewer irritants as a non-bio.

Is biological washing powder environmentally friendly?

In tests, biological formulations are more effective at cleaning than non-bio ones which may mean that you are less likely to have to re-wash or use excessive amounts. Fabric looking newer for longer might mean you keep clothes longer. Using enzymes also means that much smaller amounts of surfactant are needed. Some enzymes are effective at very low temperatures too and washing cooler can save a lot of energy. Here, you can read why one manufacturer Ecover, thinks enzymes are a good thing.

Is it true that enzymes don’t work above 40 degrees Celsius?

No. While this is true of the enzymes inside our own bodies, enzymes for cleaning are extracted from a variety of sources in order to take advantage of different properties, such as working at high or low temperatures or surviving in the alkaline conditions of washing. The ones which work in hot conditions come from bacteria that live in hot springs.

Should I change to biological washing powder?

That’s up to you! At Nappy Science Gang we’re interested in trying to reveal useful facts by questioning received wisdom, talking to qualified experts, and consulting scientific evidence, so you can make your own informed decisions. You can join in the discussion and be part of the science by joining our Facebook group or one of our live expert chats at .

A note on the content of this article: a lot of our working knowledge has been built by questioning experts in the field in our Nappy Science Gang live chats (full list). The following chats in particular have informed this article: 

2 thoughts on “Nappy Leaks: Bio Hazard?

  1. This is a very interesting article. The next step is to speak to supermarkets as they al have big labels explaining to mums that bio-detergents cause more skin irritation.


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