Skin allergenicity of airborne and soil algae isolated from Malaysia

Studies have shown that the aquatic algae can cause allergy in humans. However, there are relatively few studies of airborne and soil algae on skin allergenicity. Therefore, we aimed to assess the skin allergenicity potential of airborne and soil algae isolated from Malaysia. Six algal species namely Scenedesmus sp., Stichococcus sp., Chlorococcum sp., Chlorella sp., Ulothrix sp. and Hapalosiphon sp. isolated from air and soil samples were screened based on the expression of IL-18 by NCTC 2544 keratinocytes in vitro assay. The mechanism of Stichococcus sp., Hapalosiphon sp. and Scenedesmus sp. in inducing skin allergenicity was further elucidated using Balb/c mouse model. Both proliferation of T-lymphocytes at local lymph nodes and expression of various acute inflammatory cytokines were assessed. The in vitro study showed that all algal extracts (1 mg/mL) except Ulothrix sp. were potential contact sensitisers and induced the expression of IL-18 by 0.369–5.227 pg/mg (IL-18/unit protein) in NCTC 2544 cells. The in vivo study revealed that Scenedesmus sp., Hapalosiphon sp. and Stichococcus sp. were able to induce skin sensitisation in mice with a stimulation index (SI) greater than 1.6 in the local lymph node assay (LLNA) suggesting these three algae species can cause allergic contact dermatitis (ACD). In addition, they are able to stimulate the expression of acute inflammatory cytokines such as GM-CSF, IL-1α and TNF-α. It was concluded that airborne and soil algae are potential contact allergens and can cause allergic contact dermatitis.