Parthenium dermatitis in India: past, present and future.

Parthenium dermatitis is an immuno-inflammatory disease caused by Parthenium hysterophorus and is the commonest cause of plant dermatitis in 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. The combined type IV and type I hypersensitivity to parthenium has been recently postulated. In sensitized individuals, it can cause a spectrum of clinical patterns, such as classical airborne pattern, chronic actinic dermatitis-like presentation, mixed pattern dermatitis, exfoliative dermatitis, widespread dermatitis, and other rare patterns. There is definite trend towards change from airborne pattern to chronic actinic pattern in natural history of parthenium dermatitis. Contact sensitivity to parthenium is everlasting, and hence the disease runs a chronic course with exacerbation during summers. Patch testing with acetone or aqueous plant extract is the simplest way of confirming parthenium contact allergy. Management includes avoiding contact with allergen, managing dermatitis with topical corticosteroids/tacrolimus, and other immunosupressives like azathioprine. In future, we expect parthenium dermatitis to become less prevalent due to rapid urbanization and possible development of new biological methods to eradicate the parthenium. Genetic factors associated with susceptibility to parthenium dermatitis need to be studied.

Contact dermatitis to hair dye: an update.

Exposure to hair dyes has long been known as a significant risk factor for development of allergic contact dermatitis among the exposed population as these lead to severe eczema of face and upper trunk in the consumer and hand eczema in hair-dressers. Currently, para-phenylenediamine (PPD) is the main ingredient used in permanent hair color products in the market and is the most important allergen. Prevalence of PPD sensitization is high in patients with contact dermatitis across all continents, with hair dye use being the commonest cause. In order to decrease the burden of disease, use of alternative natural dyeing agents among consumers and use of barrier neoprene gloves among hairdressers should be encouraged apart from stringent legislation to reduce the amount of PPD reaching the consumer.

Contact allergy to topical corticosteroids and sunscreens.

Topical corticosteroids and sunscreens are extensively used formulations, both as over-the-counter products and as prescription medicines. Topical corticosteroids are increasingly being recognized as causes of allergic contact dermatitis. Because of their anti-inflammatory property, contact allergy to these agents may be difficult to suspect and prove. With corticosteroid allergy, there are special issues in patch testing that need to be considered: Screening tests need to be done with budesonide and tixocortol pivalate, and delayed readings are essential to pick up all positive cases. Preventive advice needs to be tailored according to the structural and chemical peculiarities of a particular molecule. Sunscreen allergy is a significant part of cosmetic allergy; especially in cases of photoallergic reactions. Each passing decade is bringing forth new allergens in this class. In many countries, benzophenones have recently been replaced by octocrylene as the leading causes of contact dermatitis to sunscreens. This article provides a broad overview of corticosteroid and sunscreen allergy so that the readers are aware of these important emerging classes of allergens.

Relationship between nickel allergy and diet.

Nickel is a ubiquitous trace element and it occurs in soil, water, air and of the biosphere. It is mostly used to manufacture stainless steel. Nickel is the commonest cause of metal allergy. Nickel allergy is a chronic and recurring skin problem; females are affected more commonly than males. Nickel allergy may develop at any age. Once developed, it tends to persist life-long. Nickel is present in most of the dietary items and food is considered to be a major source of nickel exposure for the general population. Nickel content in food may vary considerably from place to place due to the difference in nickel content of the soil. However, certain foods are routinely high in nickel content. Nickel in the diet of a nickel-sensitive person can provoke dermatitis. Careful selection of food with relatively low nickel concentration can bring a reduction in the total dietary intake of nickel per day. This can influence the outcome of the disease and can benefit the nickel sensitive patient.