Acetylcholine is released from a presynaptic neuron into the synaptic cleft. Once in the synaptic gap, acetylcholine can: - Bind to presynaptic receptors: presynaptic activation or inhibition leads to automodulation of the presynaptic cholinergic neuron.
When welts are a sign of a medical problem, they are usually accompanied by other symptoms which provide clues to the problem. Physical trauma such as a blow can cause a welt, and welts can also be caused by allergic reactions, infections, injections, insect bites, and skin reactions, in very sensitive people. For example, in people with dermographism, even a gentle touch to the skin can cause a welt to emerge.
Allergy is a common cause of a skin rash that appears as welts. Welts are raised, red or skin-colored blisters and lesions on your skin of varying shapes and sizes. If you have a full body rash characterized by welts, you may have hives. Allergies can produce hives, a condition that typically is not life-threatening; however, other symptoms of an allergic reaction can be fatal.