Dyes in soaps, lotions and detergents: do they matter for your skin?

“Free of dyes” sits right next to “fragrance-free” on a lot of packaging, as if the two were equal partners. They aren’t. Fragrance is one of the biggest causes of skin allergy from everyday products. Colourants, the dyes and pigments that make a body wash blue or a detergent green, are near the bottom of the list. Here’s why they’re there, why the real dye allergy comes from somewhere else, and why skipping them can still make sense.

Why are dyes in these products at all?

A colourant does one thing: it makes the product look the way the company wants it to look. A pale blue cleanser reads as fresh, a golden shampoo looks rich, a pink lotion looks gentle. None of that changes how the product cleans or moisturizes. A dye is there for your eyes, not for your skin.

In Canada, colouring agents in cosmetics have to appear in the ingredient list like everything else. Health Canada’s labelling guide explains that they can be listed by name or by Colour Index number, the code that looks like “CI 42090”, and that all colouring agents, whatever their concentration, may be listed together after the ingredients present at more than 1%. That’s why you’ll usually find them clustered at the very end. For makeup sold in a range of shades, a company may list every colourant used across the range, preceded by “may contain” or a “±” sign.

So the dyes aren’t hidden. If you want to know whether your cleanser has one, look for “CI” plus five digits, or a colour name, near the bottom of the list.

How often do dyes in skin care actually cause allergy?

Rarely, especially compared with the ingredients around them.

Allergic contact dermatitis is an itchy, red, often scaly rash that appears when your immune system has learned to react to a specific substance. DermNet’s overview of cosmetic reactions ranks the usual suspects: fragrances are the most common source of contact dermatitis from cosmetics, preservatives are the second most common, and the hair dye chemical paraphenylenediamine (PPD) is third. Ordinary colourants in cleansers and lotions don’t make the list. DermNet also notes that about 80% of all cosmetic reactions are irritant rather than allergic, meaning the product was simply too harsh for that skin on that day.

PPD is a real dye allergy, but it’s a special case: it’s a reactive chemical used in permanent hair colour and left to work on the scalp, which is nothing like the trace of colourant in a body wash.

What about the dyes in laundry detergent?

Laundry detergent gets blamed for a lot of rashes. A 2023 review in the journal Cutis found that 10.7% of 738 patients undergoing patch testing believed detergent was contributing to their skin problem. When the North American Contact Dermatitis Group actually tested those 738 patients with diluted detergents, only five, or 0.7%, had a possible allergic reaction, and further testing suggested some of those were irritant reactions rather than true allergy. The authors concluded that detergent allergy was “at most 0.7%, and possibly lower.”

The same review lists the potential allergens in detergents: fragrances, preservatives, surfactants, emulsifiers, bleaches, brighteners, enzymes and dyes. When researchers analyzed detergents sold in the United States, the allergens that turned up most often were fragrances and preservatives. Dyes were on the list of possibilities, not at the top of it.

There’s also a practical reason. Detergent gets rinsed away, and the review notes that machine washing appears to reduce allergen levels on fabric to below what usually matters clinically, though the authors are careful to say that uncertainty remains for people with strong allergies.

The dye allergy dermatologists really see: disperse dyes in clothing

If you want to find the dye allergy that genuinely affects people, look at the clothes, not the wash.

Disperse dyes are the colourants used for synthetic fabrics such as polyester and acrylic. DermNet explains that they don’t bind tightly to the fibre; sweat leaches the dye out, so it migrates onto your skin wherever the fabric rubs and you perspire. Disperse Blue 106 and Disperse Blue 124 are the best-known offenders, so much so that the American Contact Dermatitis Society named the disperse blue dyes its Contact Allergen of the Year in 2000.

The numbers back this up. A 2013 review in the journal Contact Dermatitis looked at 54 studies covering 26 disperse dyes and found that the average rate of positive patch tests in screening studies was above 1% for Disperse Blue 106, Disperse Blue 124 and Disperse Orange 3. The Cutis review adds that between 2017 and 2018, 2.3% of 4,882 patients patch tested by the North American Contact Dermatitis Group reacted to a disperse dye mix, and notes that the true figure may be higher because standard test kits don’t catch every dye.

The pattern of the rash is the giveaway. DermNet describes it as appearing where clothing touches the skin, worse where there’s rubbing and sweating: the waistband, upper thighs and buttocks. The Cutis review adds a classic sign for dermatologists: a rash along the rim of the armpit that spares the hollow, because the hollow doesn’t touch the sleeve.

If this sounds like you, the fixes are simple. DermNet suggests washing new clothing at least three times before wearing it and favouring light-coloured garments made from natural fibres such as cotton, linen or wool. Patch testing can confirm the diagnosis.

So why choose dye-free anyway?

Because it costs you nothing and it removes one more variable.

If you have eczema (atopic dermatitis, a chronic condition where the skin’s outer barrier is weaker and lets more of what touches it get through), or skin that reacts to a lot of things, the goal is to keep the list of ingredients on your skin short. Dyes don’t clean, don’t moisturize and don’t preserve. They are pure decoration, so dropping them has no downside.

That’s the logic behind the American Academy of Dermatology’s advice for children with eczema: use only detergent that is fragrance-free and dye-free, and talk to your child’s dermatologist if you suspect a sensitivity to a dye. Notice the order, though. Fragrance-free comes first, because that’s where the real risk lives. A colourful bottle that is truly fragrance-free is a better choice for reactive skin than a clear one that says “parfum” on the back.

If you’re building a routine for sensitive skin, our fragrance-free products filter is a good starting point, and many of the items in the laundry category are free of both fragrance and dyes.

When a rash needs a closer look

Rashes have many causes, and “it must be the detergent” is a guess more often than a diagnosis. A rash that follows your clothing lines points to textile dye. One on the hands, face or armpits points to something you apply there. If a rash doesn’t improve after two weeks of switching to fragrance-free, dye-free products, see your doctor or pharmacist, and ask about patch testing if it keeps coming back.

What to remember: colourants in soaps, lotions and detergents are a rare cause of skin allergy, fragrance and preservatives are far bigger ones, and the dye allergy worth knowing about comes from synthetic clothing. Going dye-free is a sensible, cheap simplification for reactive skin, as long as you don’t let it distract you from the ingredient that matters most.