Morinda citrifolia Linn. (Rubiaceae) leaves have been used in tropical folk medicine to treat topical inflammation and burns. A carbomer gel base, containing the ethanol extract and juice pressed from the leaves, was evaluated for potential allergenic properties in a repeat-insult patch test in 49 volunteers. To investigate the topical photo-protective properties, the combined ethanol extract and leaf juice were evaluated in a UVB-induced erythema model in 25 volunteers. The crude ethanol extract of M. citrifolia leaves was also evaluated in vitro for potential anti-inflammatory activity in a histamine H-1 receptor antagonism assay. There was no evidence of allergenic potential in the repeat-insult patch test. When the combination of ethanol extract and leaf juice was applied, the UVB dose required to induce erythema was almost 3.5 times greater than with untreated skin (P < 0.001). In the histamine H-1 receptor-binding assay, the crude ethanol extract of M. citrifolia leaves inhibited receptor binding by 57%. These results suggest that M. citrifolia leaves are safe for topical use and may be useful in mitigating UVB-induced injury to the skin.