Preventing pink and brown stains in textiles by understanding your laundry process

A towel, bathrobe or item of bed linen may arrive at the laundry looking clean, with perhaps only slight yellowish or greasy discolouration. However, after washing, striking pink, red, brown or rust-coloured stains may suddenly appear. Because the discolouration only becomes visible during the wash process, identifying its cause is not always straightforward. Pink or brown stains appearing after washing are often caused by a combination of product residues, water quality and process conditions.

This is a particular risk for laundries serving hotels, resorts, wellness facilities and cruise ships. Guests protect themselves from harmful UV radiation and use a wide range of sunscreen brands and product types. Their composition varies from product to product, while the textiles involved are often white or light-coloured and undergo frequent or intensive washing. The question is therefore not only how an existing bright-pink or brown stain can be removed, but more importantly: can our laundry process remove sunscreen residues effectively before they cause problems?

Why sunscreen can cause bright-pink stains

Recent scientific research from Durham University provides more insight into a striking phenomenon: red discolouration of textiles during washing the study identified a reaction between sodium hypochlorite (NaClO) and Diethylamino Hydroxybenzoyl Hexyl Benzoate (DHHB), a widely used organic UVA filter in sunscreen products, as a possible cause of this red discolouration.

Sodium hypochlorite is a commonly used bleaching agent in wash programmes for white or light-coloured textiles. Under certain conditions, it reacts with residual UV filter present in the textile. The reaction produces a chlorinated compound with an intense red colour. The researchers demonstrated that this discolouration is not simply a superficial stain, but the result of a chemical transformation of a sunscreen ingredient.

This explains why textiles can appear reasonably clean before washing, while intensely coloured stains may suddenly become visible afterwards. This can lead to additional treatment, rewashing or the rejection of affected textiles.

Not every discolouration is the same

Based on the above, bright-pink stains may be associated with sunscreen residues in textiles and a chlorine-containing bleaching step during washing. However, not every discolouration caused by sunscreen residues has the same chemical background.

Sunscreen residues can also contribute to yellow, brown or rust-coloured discolouration. In such cases, this may be related to metal ions such as iron or copper, which may originate from water, pipework, the textile itself or laundry equipment.

When additional stains appear in textiles, it is therefore important not to immediately assign one specific cause. A sound assessment starts with questions such as:

• What type of stain or discolouration is present?
• On which types of textile does it occur?
• When were these stains or discolourations first observed?
• Have any changes been made to the laundry process since then?
• Are these isolated incidents or part of a recurring pattern?
• Do they occur across all textiles being washed, or are they limited to a particular textile type, department or laundry customer?
• Are the stains removed when the textiles are washed again using the standard wash process?

A pink stain is therefore not automatically proof of one specific cause. It is, however, a clear reason to assess the laundry process critically and systematically.

From reacting to testing in advance

In practice, a problem often becomes visible only after textiles have been washed, dried and sorted. This can result in rewashing, textile rejection, customer complaints, discussions about shortages and possible replacement costs. These consequences can quickly accumulate and have a significant financial impact.

The most valuable question is therefore not only: “How do we remove this pink stain?” A better question is: “Can we determine in advance whether our wash programme removes sunscreen residues sufficiently, and whether our process conditions create a risk of unwanted discolouration?”

A reproducible test is required to answer that question. Only then can processes be compared objectively, for example after a change in detergent dosage, process time, temperature, water quality, load size or bleach type. Testing with randomly used textiles is of limited value, as the amount of contamination, the sunscreen product used and the age of the stain will vary every time.

New development: a stain test cloth for sunscreen residues

At CCD, our goal is to give professional and industrial laundries around the world the tools to measure the performance of their laundry process objectively. As part of that mission, we are developing a dedicated stain test cloth for sunscreen-related stains and discolouration. The objective is to provide laundries with reproducible data on both the removal of sunscreen residues before discolouration occurs and the risk of visible discolouration within their own processes.

What can practical testing achieve?

Consider the following practical situation: during peak season, a hotel laundry receives large quantities of white towels. Guests use a variety of sunscreen products, and textile rejection or additional wash cycles caused by pink or brown stains can create significant operational challenges.

Using a standardised stain test cloth, the effect of the laundry process on different types of sunscreen contamination can be assessed before the peak season begins. The assessment does not only consider whether discolouration occurs, but also the extent to which the original sunscreen residues are removed from the textile.

This can support:

• Assessment of existing wash programmes
• Preventive optimisation of wash programmes
• Evaluation of a new dosing system’s performance
• Independent verification of performance following changes to the detergents used
• Periodic quality control and assurance in cooperation with the detergent supplier

Objective testing provides control

Sunscreen stains and bright-pink or brown discolouration are good examples of problems that only become visible when several factors come together: the sunscreen product used, wash-water quality, the removal of sunscreen residues during the first phase of the wash programme, and the bleaching agent applied.

It is therefore important to assess the process proactively rather than responding only after stains have appeared. By monitoring laundry-process performance with suitable test materials, it is possible to establish earlier whether sunscreen residues are being removed and whether there is a risk of unwanted discolouration.

Through the development of this new stain test cloth, we aim to help laundries, hotels, wellness facilities, resorts and cruise operators identify risks more effectively, assess their processes objectively and achieve measurable improvements in stain removal. Would you like to know how effectively your laundry process removes sunscreen residues and manages the risk of discolouration? Please contact us. We would be happy to tell you more about options available for objectively assessing your wash programme.

Sources

Smith, L.G. et al., An unexpected chlorination of an organic sunscreen, Chemical Communications, 2025. The full article can be found via the following link https://pubs.rsc.org/cc/article/61/51/9314/882434/An-unexpected-chlorination-of-an-organic-sunscreen?silentauthchecked=true