Air Borne contact dermatitis (ABCD)

Air Borne contact dermatitis (ABCD)

Introduction

• Parthenium hysterophorus and less commonly by other plants is one of the most intractable problems in dermatology in India

• ABCD is a diagnosis that encompasses all photodermatoses predominantly of exposed parts of body, which are caused by substances released by plants which when released into the air, settle on the exposed skin and acted upon by UV light to cause disease.

• In India, parthenium is also known as "Congress grass" or "Congress weed," which refers to the US congress (who allocated the shipment for Pune, India)

• It is caused by airborne dry and friable plant particles including trichomes, and the most important allergens responsible for allergic contact dermatitis are sesquiterpene lactones (SQL)

Pathology

• Combined type IV and type I hypersensitivity to parthenium has been postulated. 

• It  is an immuno-inflammatory disease, which upon contact sensitization by parthenium antigen propagates as a cell-mediated hypersensitivity immune response with early sensitization phase and a subsequent elicitation phase, if antigen exposure persists.

 

Allergens in Parthenium dermatitis

• The most important allergens responsible for allergic contact dermatitis is sesquiterpene lactones (SQL)

• It is present in the leaf, stem, flower and pollen, but the highest concentrations of SQLs are present in the small glandular hairs (trichomes) present on the undersurface of the leaves and stem

Presentation

• Most of the airborne contact dermatitis starts from the eyelids, suggesting that airborne allergens initially lodge there because of the skin folds and cause dermatitis, later affects the face, especially the eyelids and/or neck, V of the chest

• A seasonal variation is initially observed with the dermatitis flaring in the summers corresponding to the growing season and disappearing in winters.

• Repeated exposures over many years may result in widespread, extensive, and eventually chronic lichenified dermatitis that may persist throughout the year.

• The involvement of both light-exposed and protected areas helps to differentiate ABCD from only sun induced eruptions ( photodermatitis) 

  Thickened lichenified skin (above)

Involvement of face, v of the neck

lichenified papules on dorsum of hand

Diagnosis

Patch testing with plant allergen is the simplest way of confirming parthenium contact allergy. 

• Photopatch test positive (In photopatch test, parthenium area is irradiated with UV light)= If redness is seen it indicates Parthenium + Sun dermatitis (Phytophotodermatitis)

look at redness on position no.2 on both sides

Treatment

Systemically, In India- Azathioprine is the commonest drug prescribed after initial steroid therapy, especially for chronic therapy in these usually long term diseases

MCQ

A 55 year old farmer with diabetes and hypertension gets 

air borne contact dermatitis. The drug of choice is

a) Corticosteroids

b) Thalidomide

c) Azathioprine

d) Cyclosporine

Ans: C