You probably bought your last bottle of washing up liquid in under thirty seconds — grabbed it, scanned the price, kept moving. Most of us do. The label, if you ever flip the bottle over, is a wall of unfamiliar chemistry written in 6-point font.

But the contents of that bottle touch your skin a hundred times a week. They sit on the dishes you eat off. They go down the drain into the rivers we swim in. So what's in there actually matters — and once you know what to look for, the label becomes much easier to read.

Here's a no-nonsense UK guide to the most common washing up liquid ingredients, the three you should watch, and what to look for if you'd rather not.

The 6 ingredients you'll see on most UK supermarket bottles

1. Water (Aqua) — usually 60–80% of the bottle. It's the carrier for everything else.

2. Surfactants — the molecules that lift grease off your plates. Surfactants come in many forms; some are gentle, some aren't. We'll get into specifics below.

3. Preservatives — needed because the moment water and organic ingredients meet, microbes want in. The question is which preservative.

4. Fragrance / Parfum — almost always synthetic in conventional brands. "Parfum" on a UK label can legally mean a cocktail of dozens of undeclared chemicals.

5. Colour / dye — purely cosmetic. Adds nothing to performance.

6. pH adjuster — usually citric acid or a similar mild acid. Generally fine.

The 3 ingredients to watch (and why)

1. Sodium Lauryl Sulphate (SLS) and SLES

These are the workhorse surfactants in most supermarket washing up liquids. They're cheap, they foam aggressively, and they cut grease quickly. They also strip oils from skin — which is why your hands feel papery after doing the dishes. For people with eczema, sensitive skin, or contact dermatitis, SLS is a known irritant. It's not banned in the UK, but the British Association of Dermatologists routinely recommends avoiding it for sensitive-skin households.

What to look for instead: surfactants derived from coconut or sugar (e.g. coco-glucoside, decyl glucoside, lauryl glucoside). These foam less dramatically but clean just as well — and don't strip your skin.

2. Methylisothiazolinone (MIT) and Methylchloroisothiazolinone (CMIT)

Two preservatives commonly used in liquid cleaners. The European Chemicals Agency has flagged both as significant skin sensitisers — meaning repeated exposure can cause allergic reactions even in people who tolerated them initially. The EU restricted CMIT in leave-on cosmetics in 2017, but they're still permitted in rinse-off household products, including washing up liquid.

What to look for instead: products preserved using fermentation-based systems (e.g. lactobacillus ferment) or naturally antimicrobial essential oils. These are gentler and don't accumulate sensitivity over time.

3. Synthetic "Parfum"

The single word "Parfum" on a UK ingredient list can legally hide hundreds of individual chemicals — including phthalates, synthetic musks, and known endocrine disruptors. UK and EU labelling law doesn't require manufacturers to disclose what's inside their fragrance blend, only that fragrance is present.

If you're concerned about hormone-disrupting chemicals (we'll cover this in detail in an upcoming guide), synthetic fragrance is the single biggest hiding place in your cleaning cupboard.

What to look for instead: products scented only with named, certified organic essential oils — e.g. "bergamot oil (citrus aurantium bergamia)" or "lavender oil (lavandula angustifolia)". When the source is named on the label, you know what you're putting on your hands.

How to read a Read The Label London washing up liquid label

Pull a bottle of our Natural Washing Up Liquid – Bergamot & Lavender off the shelf and you'll see something different. Here's the same six-category breakdown:

• Water (Aqua) — same role, same percentage range
• Surfactants — coco-glucoside and lauryl glucoside (both coconut-derived)
• Preservative — fermentation-based, no MIT or CMIT
• Fragrance — certified organic bergamot oil and grosso lavender oil, both named
• Colour — none added (the slight amber tint is from the essential oils)
• pH adjuster — citric acid

That's the full ingredient list. We named the brand Read The Label specifically because we wanted you to be able to do exactly this — flip the bottle, scan the label, and know what's in there in 30 seconds.

But does natural actually clean?

This is the question we get the most, and it's a fair one. The honest answer: yes, with one caveat.

Plant-based surfactants like coco-glucoside generate less foam than SLS-based formulas. People associate foam with cleaning power, so the first time you use a natural washing up liquid you might assume it's not working. It is — foam is mostly cosmetic. The grease-cutting happens at a molecular level you can't see.

Our formulation pairs coconut-derived surfactants with soapwort extract (a perennial herb with natural saponins) to give you proper grease-cutting on baked-on plates and oily pans. We test against equivalent supermarket brands on standard kitchen messes — burnt-on cheese, fried-egg pans, oily mince — and ours holds its own.

Quick takeaways

• Most UK supermarket washing up liquids are 60–80% water, with the rest being surfactants, preservatives, fragrance, and colour
• SLS, MIT/CMIT, and synthetic "Parfum" are the three ingredient classes worth avoiding for sensitive-skin and chemical-conscious households
• Plant-derived surfactants, fermentation-based preservatives, and named organic essential oils are the natural alternatives
• "Natural" doesn't mean ineffective — it just means you can trace every ingredient back to a plant

If you'd like to switch to a fully readable label, browse our Natural Washing Up Liquid collection — both Eucalyptus & Geranium and Bergamot & Lavender scents are formulated around the principles above.