A Whiff of Trouble: Navigating Allergic Contact Dermatitis to Fragrance
Fragrances are found in abundance in everyday life—from obvious sources such as perfumes, colognes, and air fresheners, to not-so-common sources, such as workplace exposures. Problematically, even products labeled as “fragrance free” may contain covert fragrances. Patients and physicians alike should be aware that fragrances are a common cause of allergic contact dermatitis (ACD) and that patient education is critical to treatment success. In this review, we discuss the chemistry and epidemiology of fragrance ACD, patch test considerations, skillful patient education on avoidance, and potential pitfalls for patients with fragrance allergy—all to empower treating clinicians with the knowledge to effectively address patient needs.
Practice Points
- Fragrance allergy is common due to daily exposure from many sources, ranging from personal care products and cosmetics to cleaning products, foods/spices, and workplace materials.
- More than 100 different fragrances can cause contact allergy, but patch testing in routine practice usually is limited to a few key screening allergens with important limitations.
- Fragrance avoidance is challenging, and comprehensive patient education is critical, including the provision of a list of safe products that are truly fragrance free.
Patch Test Considerations
Patch testing is essential to confirm fragrance allergy and guide treatment, but because there are so many potential fragrance allergens, there is no perfect patch test strategy. In a standard patch test series, the most important screening allergens are considered to be FMI, FMII, and BOP; tested together, they are thought to detect a large proportion of cases of fragrance allergy. Strikingly, in a large European study (N=1951), patch testing with the fragrance markers in the baseline panel failed to detect more than 40% of cases of allergy compared to testing with 26 individual fragrance allergens.17 Other studies have reported that a smaller proportion of fragrance allergies are missed by using baseline screening allergens alone.18,19 Limonene and linalool hydroperoxides also are potentially important fragrance allergens to consider adding to the patch test panel, as unoxidized limonene and linalool commonly are used in many products and could theoretically undergo auto-oxidation under use conditions.8 However, because of the high number of irritant, questionable, and potentially false-positive reactions, the Information Network of Departments of Dermatology has recommended against adding these hydroperoxides to a standard screening tray for patch testing.20 It must be remembered that a positive patch test to a fragrance does not necessarily represent ACD unless the patient has a clinically relevant exposure to the allergen.21
In patients who test negative to the baseline fragrance-screening allergens and in whom a high degree of suspicion remains, further testing with supplemental fragrance allergens (commercially available from patch test suppliers) is warranted.17 The thin-layer rapid use epicutaneous (T.R.U.E.) test (SmartPractice) includes FMI and BOP but not FMII or linalool or limonene hydroperoxides. More comprehensive patch test panels are available that include additional fragrances, such as the North American 80 Comprehensive Series and the American Contact Dermatitis Society Core Allergen Series.22-24 It is important to remain vigilant and consider expanded patch testing if patients initially test negative but suspicion remains.
Furthermore, patch testing with the patient’s own products is an important consideration. Uter et al25 evaluated patch testing using patients’ perfumes, deodorants, and shaving lotions, and approximately 41% (53/129) of patients who tested positive to their own product tested negative for fragrance-screening allergens. Although it can be difficult to ascertain which exact component of a commercial product is the culprit, a positive patch test may still provide clinically relevant information for patients and treating physicians. In cases of questionable or weak-positive results, repeat testing or repeated open application tests can help re-evaluate suspected products.
Cross-reactivity should be considered when patch testing for fragrances. Atwater et al10 found that cross-reactivity between FMI, FMII, and BOP was common; for instance, approximately 40% of patients testing positive to FMII or BOP also had positive reactions to FMI (522/1182 and 768/1942, respectively). Understanding this concept is important because in some cases (as detailed below) patients will need to avoid all fragrances, not just the ones to which they have previously been exposed, given the limitations on fragrance labeling in the United States. However, this may change with the Modernization of Cosmetic Regulation Act of 2022.26
