This international study is based on four nationally representative cross-sectional surveys of adults ages 18–65 in the US, AU, UK, and SE. Sample populations (n = 1137, 1098, 1100, 1100, respectively) were representative of the general populations according to age, gender, and region (confidence limit = 95%, margin of error = 3% for all studies). Using randomized participant recruitment, the surveys drew upon large web-based panels (with over 5,000,000; 200,000; 900,000; 60,000 participants, respectively) held by Survey Sampling International. For the panels, SSI uses multi-source samples to develop a blend that reflects the heterogeneity of the study population. For the surveys, recruitment followed a three-step randomization process to identify potential participants (see Electronic Supplementary Materials (ESM-Methods and ESM-SSI)). The survey instrument, the same questionnaire in each country’s native language, was developed and tested over a two-year period before full implementation in June 2016 (US, AU, UK) and June 2017 (SE). The survey response rates were 94%, 93%, 97%, and 92% (respectively), and all responses were anonymous. Descriptive statistics and cross-tabulations determined percentages according to each response and sub-population; see Electronic Supplementary Material (ESM-Data). The research study received ethics approval from the University of Melbourne. Survey methods are detailed in the Electronic Supplementary Material (ESM-Methods).
To promote comparability, the survey replicated questions from previous studies of fragrance sensitivity (Steinemann 2016, 2017a, 2018a, b, c, d, 2019; Steinemann et al. 2018; Caress and Steinemann 2009), as follows.
For fragrance sensitivity, the survey asked, “Do you experience any health problems when exposed to (fragranced product)?” If the respondent answered yes, the survey then asked about which health problems they experienced. An individual was considered to characterize fragrance sensitivity if they reported one or more types of health problems from exposure to one or more types of fragranced consumer products.
Fragranced products were categorized as follows: (a) air fresheners and deodorizers (e.g., sprays, solids, oils, disks); (b) personal care products (e.g., soaps, hand sanitizer, lotions, deodorant, sunscreen, shampoos); (c) cleaning supplies (e.g., all-purpose cleaners, disinfectants, dishwashing soap); (d) laundry products (e.g., detergents, fabric softeners, dryer sheets); (e) household products (e.g., scented candles, restroom paper, trash bags, baby products); (f) fragrance (e.g., perfume, cologne, after-shave, essential oils); and (g) other.
Exposure contexts included the following: air fresheners or deodorizers used within indoor environments; scented laundry products coming from a dryer vent; being in a room after it was cleaned with scented cleaning products; being near someone wearing a fragranced product; and exposure to other types of fragranced consumer products.
Health effects were categorized as follows: (a) migraine headaches; (b) asthma attacks; (c) neurological problems (e.g., dizziness, seizures, head pain, fainting, loss of coordination); (d) respiratory problems (e.g., difficulty breathing, coughing, shortness of breath); (e) skin problems (e.g., rashes, hives, red skin, tingling skin, dermatitis); (f) cognitive problems (e.g., difficulties thinking, concentrating, or remembering); (g) mucosal symptoms (e.g., watery or red eyes, nasal congestion, sneezing); (h) immune system problems (e.g., swollen lymph glands, fever, fatigue); (i) gastrointestinal problems (e.g., nausea, bloating, cramping, diarrhea); (j) cardiovascular problems (e.g., fast or irregular heartbeat, jitteriness, chest discomfort); (k) musculoskeletal problems (e.g., muscle or joint pain, cramps, weakness); and (l) other.
Societal effects included the following: ability to access restrooms, businesses, public places, and other locations that use air fresheners or fragranced products; disabling effects; lost workdays or lost jobs due to fragranced product exposure; associated economic costs; and preferences for fragrance-free environments.