Laundry detergent, a cleaning agent ubiquitous in the modern household, often is suspected as a cause of allergic contact dermatitis (ACD). In one North American study, 10.7% of 738 patients undergoing patch testing believed that laundry detergent was a contributing factor, whereas their referring physicians had the same concern less often (in 2.3% of cases).1 Likewise, in a 1992 survey of western US households, more than 20% of 3841 respondents reported skin or health problems attributed to a textile and/or laundry product.2 The suspicion of laundry detergent as a causative agent of ACD is perpetuated across popular wellness and beauty websites.3,4 Does the evidence support this degree of suspicion? Or, similar to the well-meaning parent who misguidedly fixates on foods as the cause of their child’s atopic dermatitis and believes elimination diets are the solution,5 could a similar desire for control in the face of the unpredictability of eczema drive consumers and health care providers alike to blame laundry detergent—a familiar and modifiable cause?
We provide a summary of the evidence for the potential allergenicity of laundry detergent, including common allergens present in laundry detergent, the role of machine washing, and the differential diagnosis for laundry detergent–associated ACD.
Allergenic Ingredients in Laundry Detergent
Potential allergens present in laundry detergent include fragrances, preservatives, surfactants, emulsifiers, bleaches, brighteners, enzymes, and dyes.6-8 In an analysis of allergens present in laundry detergents available in the United States, fragrances and preservatives were most common (eTable).7,8 Contact allergy to fragrances occurs in approximately 3.5% of the general population9 and is detected in as many as 9.2% of patients referred for patch testing in North America.10 Preservatives commonly found in laundry detergent include isothiazolinones, such as methylchloroisothiazolinone (MCI)/methylisothiazolinone (MI), MI alone, and benzisothiazolinone (BIT). Methylisothiazolinone has gained attention for causing an ACD epidemic beginning in the early 2000s and peaking in Europe between 2013 and 2014 and decreasing thereafter due to consumer personal care product regulatory changes enacted in the European Union.11 In contrast, rates of MI allergy in North America have continued to increase (reaching as high as 15% of patch tested patients in 2017-2018) due to a lack of similar regulation.10,12 More recently, the prevalence of positive patch tests to BIT has been rising, though it often is difficult to ascertain relevant sources of exposure, and some cases could represent cross-reactions to MCI/MI.10,13
Other allergens that may be present in laundry detergent include surfactants and propylene glycol. Alkyl glucosides such as decyl glucoside and lauryl glucoside are considered gentle surfactants and often are included in products marketed as safe for sensitive skin,14 such as “free and gentle” detergents.8 However, they actually may pose an increased risk for sensitization in patients with atopic dermatitis.14 In addition to being allergenic, surfactants and emulsifiers are known irritants.6,15 Although pathologically distinct, ACD and irritant contact dermatitis can be indistinguishable on clinical presentation.
How Commonly Does Laundry Detergent Cause ACD?
The mere presence of a contact allergen in laundry detergent does not necessarily imply that it is likely to cause ACD. To do so, the chemical in question must exceed the exposure thresholds for primary sensitization (ie, induction of contact allergy) and/or elicitation (ie, development of ACD in sensitized individuals). These depend on a complex interplay of product- and patient-specific factors, among them the concentration of the chemical in the detergent, the method of use, and the amount of detergent residue remaining on clothing after washing.
In the 1990s, the North American Contact Dermatitis Group (NACDG) attempted to determine the prevalence of ACD caused by laundry detergent.1 Among 738 patients patch tested to aqueous dilutions of granular and liquid laundry detergents, only 5 (0.7%) had a possible allergic patch test reaction. It was unclear what the culprit allergens in the detergents may have been; only 1 of the patients also tested positive to fragrance. Two patients underwent further testing to additional detergent dilutions, and the results called into question whether their initial reactions had truly been allergic (positive) or were actually irritant (negative). The investigators concluded that the prevalence of laundry detergent–associated ACD in this large group of patients was at most 0.7%, and possibly lower.1
Importantly, patch testing to laundry detergents should not be undertaken in routine clinical practice. Laundry detergents should never be tested “as is” (ie, undiluted) on the skin; they are inherently irritating and have a high likelihood of producing misleading false-positive reactions. Careful dilutions and testing of control subjects are necessary if patch testing with these products is to be appropriately conducted.