title: Reduced allergy rates in atopic eczema to contact allergens used in both skin products and foods: atopy and the 'hapten-atopy hypothesis'.
abstract: BACKGROUND
  Food allergy is strongly associated with atopy. This retrospective study investigates whether atopic status affects responses to contact allergens also found in food. We compared incidences of atopic dermatitis/eczema (AD) in subjects who were patch-test positive (PT+) to diallyl disulfide from handling garlic and parabens used as a skin cream/ointment and food preservative with the incidence in those subjects who were PT+ to chemicals encountered at skin surfaces (lanolin and nickel).
  
  
  RESULTS
  36,658 patients with eczema/dermatitis were patch tested (1980-2006). 10,326 (28.2%) had AD. 13/83 (15.6%) PT+ subjects to diallyl disulfide/garlic had AD (AD/total population versus AD/diallyl disulfide PT+, P = 0.011). 54/239 parabens PT+ had AD (22.6%), while 181/608 lanolin PT+ had AD (29.8%) (P < 0.05).
  
  
  CONCLUSIONS
  Contact allergy to haptens with oral and skin exposure is reduced in AD compared with non-AD, unlike food protein hypersensitivity. Lanolin frequency was not decreased. Possible explanations include (i) confounding factors, e.g. AD subjects handle garlic less than non-AD subjects, or (ii) AD patients tolerate haptens efficiently, secondary to their atopic status, or (iii) oral tolerance of haptens antagonizes tolerance of food proteins, contributing to development of atopy (hapten-atopy hypothesis). The recent upsurge of atopy took place when gut exposure to haptens in processed foods increased dramatically.
authors.affiliation: Department of Cutaneous Allergy, St John's Institute of Dermatology, St Thomas' Hospital, London SE1 7EH, UK.
authors.forename: John P
authors.initials: JP
authors.lastname: McFadden
authors.forename: Jonathan M L
authors.initials: JM
authors.lastname: White
authors.forename: David A
authors.initials: DA
authors.lastname: Basketter
authors.forename: Ian
authors.initials: I
authors.lastname: Kimber
mesh_terms: D000485:Allergens / Q000009:adverse effects; D000498:Allyl Compounds / Q000009:adverse effects; D003358:Cosmetics / Q000009:adverse effects; D016208:Databases, Factual; D003876:Dermatitis, Atopic / Q000150:complications* / Q000276:immunology; D004220:Disulfides / Q000009:adverse effects; D004739:England / Q000453:epidemiology; D005512:Food Hypersensitivity / Q000150:complications / Q000453:epidemiology*; D005520:Food Preservatives / Q000009:adverse effects; D005737:Garlic / Q000009:adverse effects; D006241:Haptens / Q000276:immunology; D006801:Humans; D015994:Incidence; D008499:Medical Records; D009532:Nickel / Q000009:adverse effects; D010328:Patch Tests; D015995:Prevalence; D012189:Retrospective Studies
chemical_list: D000485:Allergens; D000498:Allyl Compounds; D003358:Cosmetics; D004220:Disulfides; D005520:Food Preservatives; D006241:Haptens; C028009:diallyl disulfide; D009532:Nickel