No, peeing in the shower after dying your hair won’t create mustard gas

The theory was popularised on TikTok (Picture: TikTok/Goffgirl666)

Mixing chemicals in the bathroom or kitchen has always been a no-no, with some concoctions causing burns or even fatalities.

A recent TikTok, however, has highlighted that it’s not just cleaning products you need to be careful about mixing.

In the video, posted by goffgirl666, she speaks about how peeing in the shower while washing off your hair dye can actually cause a chemical reaction making mustard gas.

We love all these Brainiac (remember that show?) type factoids, but it’s not 100% true, and certainly nothing to worry about day-to-day.

Regarding the mustard gas/hair dye/pee question, a spokesperson from Public Health England told Metro.co.uk: ‘There is no evidence to suggest this is true.’

Hairdresser Lou Birkett, Co-Founder of WhiP London adds: ‘After a discussion with our hair product partner Oway, it was agreed that the levels of toxins in urine are not high enough to allow mustard gas to be created.

‘As an eco-friendly salon, at WhiP we feel positively about saving water, but while dyeing your hair we might err on the side of caution…’

Basically, while you’re not going to create mustard gas washing out your home bleach job, it’s still not a great idea to give it a go.

This is less because you can make mustard gas, and more because you’re washing the irritant bleach (albeit diluted) onto your skin. Save yourself the hassle and use a shower head to rinse off hair over the bath or sink.

When it comes to household bleach, don’t mix that with anything that contains ammonia – even your pee.

There’s a slight chance (very slight when it comes to peeing in a toilet that’s had bleach in it, but much higher in other situations) that you could create chlorine gas.

The science behind this is that pee contains ammonia which, when mixed with cleaning bleach (which contains sodium hypochlorite), can create chloramine gas.

Chloramine gas – not mustard gas, which is made using distilled mustard – is harmful when breathed in, and can cause death if inhaled in large quantities.

Hair bleach is made using hydrogen peroxide rather than sodium hypochlorite, so this reaction is extremely unlikely to occur as described in the TikTok.

Basically, there won’t be chemical warfare in your bathroom after a home dye, but you shouldn’t go around testing that theory as the consequences can be dire.

Always speak to a professional before using new dyes, do a patch test, and follow the instructions carefully.

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Get in touch at MetroLifestyleTeam@metro.co.uk.

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