Allergic contact cheilitis to garlic

A survey of plants responsible for causing irritant contact dermatitis in the Amathole district, Eastern Cape, South Africa

ETHNOPHARMACOLOGICAL RELEVANCE

Potentially harmful plants grow almost everywhere, hence, it is not practical to eradicate them all. However, a basic understanding of adverse cutaneous reactions and the common plants that cause each type can enable vulnerable individuals to discover the source of their dermatitis and thus prevent re-exposure. The aim of this study therefore, was to document the plants responsible for irritant contact dermatitis (ICD) in the Eastern Cape, along with their respective irritants and clinical presentations.

MATERIALS AND METHODS

Study participants (161) in 12 locations were selected by convenient sampling with particular focus on local people who regularly interact with plants or plant products. Interview questions were focused on the local names of plants that contain irritating chemicals and physical characteristics that cause ICD.

RESULTS

Forty four plant species distributed in 24 families and 34 genera were reported as causative agents of irritant contact dermatitis. Herbs constituted 67.35%, trees 24.49% and shrubs 8.16%. Mechanical ICD was reported to be caused by 23 species, closely followed by chemical ICD (20 species) and mechanico-chemical ICD (6 species). Species with the highest frequency of citations were Allium cepa, Acacia karroo, Capsicum annuum, Citrus limon and Zea mays. The most representative families were Euphorbiaceae (for chemical ICD), Urticaceae (for mechanico-chemical ICD), Fabaceae and Rutaceae for mechanical ICD. Most of the classes of chemical compounds identified as being responsible for chemical ICD were restricted to plants of specific genera such as the diterpenes in Euphorbia spp., disulphides in Allium spp., terpenes in Citrus spp. and isothiocyanates in Brassica spp. Thorns and hairs were reported for causing Mechanical ICD in 6 plant species each, including widely cultivated plants such as Acacia karoo and Citrus reticulata.

CONCLUSION

Irritant contact dermatitis is a common cutaneous disorder in individuals exposed to plants in the Eastern Cape, especially among workers of the food and flower industries. Health practitioners should therefore consider the possible work-related causes of dermatitis, especially in cases associated with a clear history of symptoms.

Allergic contact dermatitis to plants: understanding the chemistry will help our diagnostic approach

Allergic contact dermatitis due to plants is common. Potentially allergenic plants and plant products are found in many everyday environments, such as the home, the garden, the workplace, and recreational settings. By improving our knowledge of allergenic plant-derived chemical compounds, we will be better positioned to identify novel allergens. We review the most relevant chemical allergens that contribute to plant allergic contact dermatitis and propose a clinical classification system based on 5 major families of chemical sensitizers: α-methylene-γ-butyrolactones, quinones, phenol derivatives, terpenes, and miscellaneous structures (disulfides, isothiocyanates, and polyacetylenic derivates). We also describe the different clinical pictures of plant allergic contact dermatitis and review currently available patch test materials. A better understanding of the specific allergens involved in plant allergic contact dermatitis will help to predict cross-reactivity between different plant species or families.