Arch Dermatol
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The discovery of an itch-specific neuronal pathway, which is distinct from the pain-processing pathway, has clarified the neuronal basis for the itch sensation. Albeit being distinct, there are complex interactions between pain and itch. The inhibition of itch by pain is well known and can explain the antipruritic effect of scratching. ⋯ Conversely, blockade of spinal opioid receptors can be used as an antipruritic therapy. Moreover, the spinal processing of pain and itch can be modulated, resulting in a hypersensitivity or hyposensitivity to pain or itch: similar to chronic painful conditions, ongoing activity of pruriceptors can induce a spinal hypersensitivity for itch in patients with chronic pruritus. Therapeutic antipruritic approaches therefore should target both local inflammation and spinal sensitization of itch processing.
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Itching is defined as an unpleasant cutaneous sensation leading to the desire to scratch. It serves as a physiological self-protective mechanism as do other cutaneous sensations like pain, touch, vibration, cold, and heat to help defend the skin against harmful external agents. Pruritus can be evoked in the skin directly by mechanical and thermal stimuli or indirectly through chemical mediators. ⋯ Recent experimental studies using improved methods have demonstrated which of the suspected chemical itch mediators such as histamine, neuropeptides, prostaglandins, serotonin, acetylcholine, or bradykinin act pruritogenically on C-fibers. Moreover, investigations have revealed new receptor systems such as vanilloid, opioid, and cannabinoid receptors on cutaneous sensory nerve fibers that may modulate itch and thereby represent targets for antipruritic therapy. This review focuses on the peripheral generation of itch, including neurotransmitters, neuropeptides, and inflammatory mediators.
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Randomized Controlled Trial Clinical Trial
Laser-assisted penetration of topical anesthetic in adults.
To determine whether pretreatment of skin with erbium:YAG (Er:YAG) laser-assisted delivery facilitates the penetration of lidocaine cream to provide anesthesia suitable for needlesticks after just 5 minutes. ⋯ Treatment with the Er:YAG laser followed by lidocaine cream is a safe, effective, and efficient means of inducing skin anesthesia that significantly reduces the pain of hypodermic needle insertion.
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To develop a practical technique to distinguish autoimmune subepidermal bullous diseases. ⋯ Laser scanning confocal microscopy allows precise localization of in vivo-bound IgG in patients' skin and, thus, it is a rapid method for the differentiation of mucous membrane pemphigoid from bullous pemphigoid and epidermolysis bullosa acquisita. This tool is suitable for the routine diagnosis of individual patients and for retrospective studies. This method is of special value in those patients in whom circulating autoantibodies are not detectable.