I would use "button" instead of "label", hope this help someone.
This will just display a button, user clicked will popup file chooser, after file chose, automatically upload.
<button onclick='<%= "$(\"#" + FileUpload1.ClientID + "\").click(); return false;" %>'>The Text You Want</button>
<asp:FileUpload onchange="$('#btnUpload').click();" ID="FileUpload1" runat="server" style="display: none;" />
<asp:Button ID="btnUpload" ClientIDMode="Static" runat="server" OnClick="btnUpload_Click" style="display: none;" />