You will start with a drop shadow. With the 'blood' layer selected choose Layer>Effects>Drop Shadow to open the Effects Dialog box (shown middle right). Click on the color box to open the Color Picker Dialog. Change the RGB values to 100,0,0 and click OK. Since the blood is a liquid, we want the shadow to have a tinge of red to it. The rest of the settings are (Mode: Multiply; Opacity: 100%; Angle: 135; Distance: 5; Blur: 10; Intensity: 50). Without closing the Effects Dialog, select Outer Glow from the effects drop down box, click apply and use the following settings (Mode: Multiply; Color: RGB 100,0,0; Opacity: 75%; Blur: 5; Intensity: 50). Again, without closing the Effects, choose Inner Glow from the effects drop down box, click apply and use the following settings (Mode: Multiply; Color: RGB 100,0,0; Opacity: 50; Blur: 10; Intensity: 50; Type: Edge).
The final effect is something even Dracula would have to appreciate. I used levels to darken the background and the blood a bit. I also painted a few highlights here and there with the Paintbrush Tool and one of the Assorted Brushes.
Give it a try in green, it also makes great slime.