Allergic contact stomatitis to dodecyl gallate? A review of the relevance of positive patch test results to gallates

Gallic acid esters or gallates are antioxidants used as preservatives in food and cosmetics. Few cases of gallates causing allergic contact dermatitis (ACD) have been reported in the literature. We present a case report of a 42-year-old beauty therapist who presented with a swollen tongue. Patch testing was positive to dodecyl gallate, commonly reported as being present in edible oil and oily foods such as margarine. Our patient avoided foods presumed to contain gallates and at the 6-week review reported a substantial improvement in her tongue symptoms. We reviewed our database and found 16 (7%) definitely or possibly relevant reactions to dodecyl gallate, seven (15%) definitely or possibly relevant reactions to propyl gallate and six (3%) definitely or possibly relevant reactions to octyl gallate. Most reactions were attributed to margarine, moisturising cream and lipstick. These products are often mentioned in the literature as containing gallates; however, ingredient labelling and discussions with manufacturers made it difficult to establish whether they are currently present in foods. Ascertaining relevance for these reactions is not always possible.