Table 2.

Epidemiological studies confirming persulphates as cause of occupational asthma and/or occupational rhinitis in hairdressers, based on specific inhalation challenge as „gold “ diagnostic standard (n = 11 studies, n = 13 publications)

Author, year of publication, country	Study period, study design, respiratory outcome	Methods	N cases	N controls	Main outcomes	Quality assessment Total score*
Munoz et al. (2003) Spain	1997–2001 Prospective study OA	SPT to common inhalatory allergens, APS, PPS; total IgE; NSIC; SIC with PPS; PEF-monitoring; spirometry at follow-up	8 cases 5 hairdressers		Time between start of exposure and diagnosis: 15 y SIC + in 7; total IgE + in 6; pre-rhinitis in 6; SPT + to PS in 5 with increased total IgE IgE dependent mechanism of OA caused by PS suspected; diagnosis must be based on SIC	14
Munoz et al. (2004) Spain	1997–2002 Case–control OA	SPT to common inhalatory allergens, APS, PPS; total IgE; NSIC; SIC with PPS	Suspected OA 8 cases 5 hairdressers	8 other asthma cases 10 healthy subjects	Suspected OA: SPT + to PS in 4/8; SIC + in 6/8 (1 early, 6 late, 1 dual bronchial response) Other asthma cases: SIC + in 1/8 (late response)	13.5
Di Stefano et al. (2004) Italy, UK, USA	1993–2001 Retrospective cohort OA due to low molecular weight agents	spirometry, NSIC, PEF monitoring, SIC partially, SPT to common inhalatory allergens	98 OA cases (hairdressers not separated)		PS were cause of OA in 3 (3%) cases, with hairdressers as common occupation	9.5
Moscato et al. (2005) Italy	1996–2004 Retrospective cohort OA	SPT to common inhalatory allergens, latex, APS; patch test to hairdressing chemicals; total and specific IgE to common inhalatory allergens and latex), spirometry, NSIC, SIC with APS, sputum induction	47 hairdressers		OA established in 24 (51.1%) cases, PS as cause in 21 (87.5%); SPT to APS negative; Bronchial response in SIC + : early 4/late 14/dual 3; Eosinophylic airway inflammation prevailed in induced sputum	12.5
Airaksinen et al. (2008) Finland	1997–2003 Retrospective cohort ORh	SPT to common and occupational inhalatory allergens; SIC with hair bleach powder	2067 (hairdressers not separated)		SIC with bleach (n = 82): nasal response + in 8, bronchial response + in 11 cases; SPT + to PS 1/67; PS was most common agent causing ORh in hairdressers	10
Diab et al. (2009) Jonsson et al. (2009) Karedal et al. (2010) Sweden	Case–control ORh	SPT to common inhalatory allergens; SIC with PPS; nasal lavage, specific IgE to PS, blood tests, flow-citometry, PCR for gene IL-5, IL-13, IFN-Y	15 hairdressers with ORh to bleach	14 hairdressers without rhinitis 12 atopics (non-hairdressers)	Hairdressers with ORh had post challenge increase in nasal symptoms and amount of albumin in lavage; no positive SPT or specific IgE to PS Hairdressers with ORh and atopics differ in post SIC parameters in nasal lavage: increase in IL-13 only in atopics, in IFN-Y only in hairdressers with ORh, in IL-5 both; apolipoprotein A1 increased only in hairdressers with ORh	12.5 12.5 14
Moscato et al. (2010) Italy	1996–2008 Retrospective cohort OA, ORh	SPT to common inhalatory allergens, latex, APS; patch test to occupational allergens; NSIC; SIC with APS; nasal lavage, induced sputum	25 hairdressers with OA to PS		OA only established in 46%, OA + ORh in 53% SPT to APS negative; patch test to APS + in 8; Bronchial response in SIC: early 33%, late 66%; Nasal response in SIC: early 64%, late 36%; Eosinophils in nasal lavage and sputum in 90% of cases	14
Kronholm Diab et al. (2014) Sweden	Prospective study ORh	Clinical inteview, SPT to PPS, nasal lavage (ECP, albumin, triptase); diary; QoL questionnaire; SIC	17 hairdressers with ORh to bleach	19 hairdressers without rhinitis 10 atopics (non-hairdressers)	Hairdressers with ORh had increase in nasal symptom score and ECP in nasal lavage during 4 weeks at work, no change in SIC; SPT to PPS negative	11.5
Hagemeyer et al. (2015) Germany	2003–2014 Retrospective cohort OA	SPT to common inhalatory allergens, APS; NSIC, SIC with APS; patch test with APS; total IgE, eNO, thorax X-ray	8 OA cases caused by PS 7 hairdressers		Comparison of 2 SIC protocols (4 and 6 steps); 6 atopics; 4 SIC + , all late response, 1 SPT + to APS; 3 out of 4 patch test + to APS; eosinophils increased in blood in 8;	12.5
Foss-Skiftesvik et al. (2016) Denmark	2014–2016 Case–control OA, ORh	SPT to common inhalatory allergens, latex, chlorhexidin, APS, PPS, SPS; total IgE; NSIC, FeNO, SIC with PPS	20 hairdressers with nasal and bronchial symptoms	14 non-hairdressers with nasal and bronchial symptoms 40 healthy subjects	SIC + in 6/19 hairdressers with: normal total IgE, atopy 4/6, rhinitic response 6/6, bronchial response 2/6, immediate reaction 4/6, immediate + late 1/6, late 1/6, SPT negative to all three PS	14.5
Nielssen et al. (2016) Sweden	Cross-sectional ORh, OA	SPT to common inhalatory allergens and PPS, spirometry, SIC in chamber with 3 consecutive bleaching procedures (symptom score, peak nasal inspiratory flow, nasal lavage, blood measurements- haemoglobine, differential blood count, IL-6, IL-8, TNFα)	12 hairdressers with rhinitis to bleach (6 exposed to dust-free bleaching powder, 6 to regular bleaching powder)		Both groups develop asthma-like symptoms after exposure; no changes found in eye and nasal symptoms, spirometry, nasal flow; increase in neutrophils, lymphocytes, monocytes after SIC in both groups; IL-8 increase in nasal lavage in both groups	10.5

PS persulphates, APS ammonium persulphate, PPS potassium persulphate, SPS sodium persulphate, OA occupational asthma, ORh occupational rhinitis, SPT skin prick test, SIC specific inhalation challenge, NSIC nonspecific inhalation challenge, FeNO fraction of exhaled nitric oxides, eNO exhaled nitric oxides, IgE immunoglobulin E, PEF peak expiratory flow, IL interleukine, IFN Y interferon gamma, TNF α tumor necrosis factor alfa, ECP eosinophil cationic protein, QoL quality of life, PCR polymerase chain reaction

*Maximum score = 15; scores ≥ 70% of maximum score are in bold