Lower incidence of sesquiterpene lactone sensitivity in a population in Asia versus a population in Europe: an effect of chrysanthemum tea?

Sesquiterpene lactones (SLs) (Fig. 1) are an important cause of allergic plant contact dermatitis but are uncommon in the Far East. They belong to the Compositae family of plants. Sensitivity to SL may be airborne or via the topical route [topical herbal remedies, cosmetic products, and in many occupations such as gardeners and florists].

Oral tolerance to contact allergens: a common occurrence? A review.

Experimental and clinical oral tolerance to contact allergens has been reported sporadically, most notably in respect of nickel, and is generally assumed to be an uncommon phenomenon. There has recently been increased understanding of the immunological mechanisms inducing and maintaining oral tolerance. There are several contact allergens, including fragrance, antioxidant, and preservative chemicals, to which subjects are exposed through both cutaneous and oral routes. We examine the possibility that oral tolerance to contact allergens may be more common than previously thought. Animal models of oral tolerance to contact allergens indicate that cutaneous exposure to small, subsensitizing doses of contact allergens might negate any subsequent attempts to induce tolerance by oral administration. Extrapolating these observations to common human practises raises the possibility that application of contact allergens (fragrances, preservatives and antioxidants) in consumer products used by children could prevent or inhibit the later acquisition of specific tolerance resulting from 'natural' dietary exposure after weaning. Existing data on formaldehyde may conflict with this theory, though this could be explained by allergen specificity. We propose that further work in this area is needed.