Purple yam (Dioscorea alata L.) is a source of biological tubers not been used optimally. Diosgenin is steroids saponin compounds that most important because it has multiple biological functions, such as allergenic activity. The objective of this research was to analyze the potential allergenic ethanol extract tuber of D. alata L. (EEDA) on BALB/c mice on sensitivity phase with measure the pro le of transcription factor FoxP3 Treg cells and cytokine pro le of Treg and IgE and IgG1 B cells. An experimental study using BALB/c mice divided into 7 groups: control group (I), the treatment group (II-V) ethanol extract of tuber Dioscorea alata L. dose of 0.00; 0.17; 2.01; 10.04 g/kg bw, the treatment group antihistamines drug and Diosgenin (VI-VII). For 17 consecutive days the group II-VII were treated in accordance with the group and with Ovalbumin induced allergy models. Mice were sacri ced on day 18. Spleen is removed, lymphocyte isolated and analyze the transcription factor FoxP3 Treg cells, cytokine pro le of T reg cells and IgE and IgG1 B cells on spleen using Flowcytometry FACS Calibur. The results showed EEDA able to inhibit the production of B220IgE and B220IgG1, trigger Treg cells (CD4CD25) and the transcription factor FoxP3 (CD4CD25FoxP3) and pro le of the cytokines produced by T reg cells. The conclusion is ethanol extract tubers of Dioscorea alata L (EEDA) does not trigger Treg (CD4CD25) and the transcription factor FoxP3 (CD4CD25FoxP3) and cytokine pro les produced by Treg cells namely CD4IL-10, CD8IL-10, CD4TGF-β and CD8TGF -β in the sensitivity phase.