Following epimucous application of corticosteroids on the lips, narrowing and shortening of the terminal network of vessels occurs within 5–7 min. The decrease in infrared radiation needs a few more minutes. Contrary to the application of epinephrine-like substances, the change of the vessels occurs first in the superficial layers and only later on in the deeper layers. In addition to the effect on the muscles of the vessels, a narrowing of the capillaries can also be influenced by the effect of corticosteroids on the endothelial cells. Changes of the ground substance of the capillary vessel bed are also a possibility.