Indusium: the case made by an insect larva: a membranous layer of the embryo of Locustidae below the serosa. Explanation of Terms Used in Entomology John. B. Smith. serosa: the outer membrane that envelops the forming embryo, the amnion and the remainder of the egg. Explanation of Terms Used in Entomology John.
In essence, your body forms an allergic reaction to stress. Unfortunately, stress can not be eliminated with histamine, so instead, the histamine just causes hives to appear on your face, neck, chest and other parts of your body.
Physical urticaria: Hives caused by direct physical stimulation of the skin -- for example, cold, heat, sun exposure, vibration, pressure, sweating, and exercise. The hives usually occur right where the skin was stimulated and rarely appear elsewhere. Most of the hives appear within one hour after exposure. Dermatographism: This is a common form of physical urticaria where hives form after firmly stroking or scratching the skin. These hives can also occur along with other forms of urticaria.