Feeding the Skin? Foods in Personal Care Products and the Risk of Allergy.

The interrupted skin barrier seen in atopic dermatitis (AD) increases exposure to environmental antigens including those in food, which contributes to the increased prevalence of food allergies in the AD population. This relationship is further explored in the dual allergen exposure hypothesis, which examines the differences in immune system response between cutaneous and oral exposures. It was previously thought that avoiding early oral exposure would decrease the likelihood of developing food allergy; however, several studies have demonstrated that earlier oral exposure increases tolerance. On the other hand, exposure to food antigens through the skin activates the helper T-cell 2 pathway, which promotes development of allergy. There have also been several studies demonstrating that aggressive treatment of AD decreases the risk of developing food allergies. Based on these findings, there is concern that inclusion of food-based ingredients in personal care products, such as moisturizers that act as main components of AD treatment regimens, may increase the likelihood of developing allergies to the included foods. However, there are many commonly used food-based ingredients that have low rates of allergy, which raises the question of why some antigens are more likely to result in allergic sensitization while many others remain benign.