• up to 20% of gen pop suffer from contact allergy

• 5-19 cases of occupational contact dermatitis / 10 000 full time workers/year

• most affected industries

  • food handler/chef

  • hairdresser/beautician

  • healthcare/vet

  • agriculture/florist/gardener

  • cleaning/laundry

  • painting

  • mechanical/engineer

  • printing/lithogaphy

  • construction

• encompasses

contact irritant dermatitis

• subjective irritancy

  • stinging within minutes of contact without objective findings

• acute contact dermatitis

  • chemical burn

• chronic contact irritant dermatitis

  • phsyical/chemical damage overwhelms skin’s repair mechanisms

• irritants

  • over and underhydration

  • soaps

  • detergents

  • solvents

  • abrasives

  • acids

  • alkali

• likelihood

  • depends:

    • potency of irritant

    • occlusion

    • temperature

    • anatomical site

    • innate susceptibility

• noramlly cumulative effect of multiple irritants

• most common affects the hands

investigation

• diagnosis based on history

• affected sites exposed to irritants with sufficient frequency, duration/conentration

• dermatitis resolves/improves following reduction or cessation of irritatn exposure

• no alternative

Management

• reduce exposure

• use of moisturising creams

contact allergic dermatitis

• small % exposed to an allergen

• many years of uneventful exposure may precede sensitisation

• once sensitised -> tiny exposures can induce dermatitis

• cell mediated immune reaction

  • dermatitis 1-4d after contact with allergen

• hands/face

  • also include sites where small amounts of allergen have been transferred accidently

• allergens:

  • rubber

  • chromate

  • epoxies

  • nickel

  • hair dies

  • fragrances

  • biocides

  • plant derivatives

    • colophony (resin)

investigation

• patch testing

• haptens applied under occlusion to intact skin for up to 48hrs

• sites checked for signs of reaction

• checked again d4, 6,7

Management

• complete avoidance

  • even tiny exposures may cuase flare

contact urticaria

• igE mediated

• non-immuniological mechanims(more common)

• immediate:

  • itching

  • welts

  • aggravation of eczema at site of exposure

• occ. generalised urtifaria

• raw meat, fish, vege

• also caused by rubber latex

investigation

• scratch-patch testing

• prick tests

• RAST

photocontact dermatitis

• sub-exposed sites

• skin altered by UV to produce

  • photoallergen

    • dermatiits through immunologic mechanisms

  • phototoxin

    • deramtitis through non immunooogic mechanisms

• most due to sunscreen chemcials

• also parsnip and celery

systemic contact dermatitis

• with contact allergy eposed to that substance systematically