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.
Angioedema is the medical term for one type of skin disorder caused by an allergy. Angioedema causes welts that may feel itchy and painful. Although this allergic reaction frequently causes reactions in the skin around your eyes and lips, it can also affect your hands and feet.Animal dander, shellfish, berries, eggs, insect bites, pollen and antibiotics, as well as other substances, may cause angioedema in people with allergies to these substances.he exact cause of this type of eczema is unknown, although people who have allergies are more likely to develop this condition. One of the main symptoms of dyshidrotic eczema involves the appearance of blisters along your fingers, hands and feet. These small blisters contain fluid and can cause intense itching.