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.
Allergies to nuts may cause skin welts. Allergies to eggs may cause skin welts. Allergies to dairy products may cause skin welts. Hives that are accompanied by other symptoms such as a swollen tongue or throat should be addressed by a doctor immediately. Allergies to shellfish, like oysters, can cause skin welts.