Agarum cribrosum Maxim, a brown algae, is an edible seaweed widely distributed across sub-tidal zone in Northeast Asian countries. A. cribrosum has known to have antioxidant and nitric oxide (NO) inhibitory activities. Trifuhalol A is a compound isolated from of A. cribrosum. In this study, trifuhalol A, a phlorotannin, was used to determine the efficacy on allergic inflammation in several allergic model such as house dust mite (HDM)-induced atopic dermatitis (AD) in mice. Trifuhalol A alleviated the symptoms such as scratch, edema, and keratinization in AD mice induced by HDM for 4 wks. A TEWL (trans-epidermal water loss) was applied to determine the severity of skin barrier function damage. Trifuhalol A reduced TEWLs of HDM-sensitized mouse dorsal skin, while increased its hydration. In addition, infiltration of inflammatory cells into dermis determining the blood levels of IgE and IL-4 was significantly reduced, which plays an important role in the expression of AD. Trifuhalol A was confirmed to reduce IgE and IL-33 in B cell and keratinocyte, which inhibit the degranulation of basophil or mast cell. Therefore, trifuhalol A might be applied as a potential therapeutic agent for allergic inflammation.