By Gary M. White, MD
Chronic scratching removes melanocytes and leaves white scars.
Pruritus is the medical term for itching. See itching for an in-depth discussion of the possible causes.
The following discusses the different categories of therapy for itching. Of course, knowing the actual cause is paramount in directing therapy. One may go through the list below in a stepwise manner.
Moisturizing the skin can be very effective in reducing itch, particularly if the itch is caused by dry skin, eczema, or contact dermatitis. The patient should be instructed to shower daily and then apply a topical moisturizing cream, e.g., Eucerin, Cetaphil, immediately after for 7 days. See dry skin handout.
Topical steroids can be very effective at reducing the itch caused by inflammatory skin disorders, e.g., eczema, psoriasis. The patient should be instructed to shower daily and then apply a topical steroid ointment, e.g., fluocinonide ointment, immediately after. Do this for 7 days. Call you with the results.
If hives or dermatographism is the cause, then antihistamines are the treatment. A 5-day trial of cetirizine (Zyrtec) 10-20 mg BID for uncertain cases is appropriate.
UVB is the go-to treatment when all else fails. It can be very effective for idiopathic cases, or those caused by renal or hepatic dysfunction. A study comparing UVB to UVB plus UVA did not show any benefit to the addition of UVA [JEADV 2017;31;1208].
For significant diffuse pruritus of unknown cause that responds to systemic steroids, azathioprine can be very effective [J Am Acad Dermatol 2015.05.025]. In this report of 96 such patients, itch score went from 9.3 pretreatment to 1.6 posttreatment. A typical dose in that study was 150 mg/day.
Topical calcineurin inhibitors (TCIs), tacrolimus and pimecrolimus, can reduce pruritus in patients with AD, chronic irritant hand dermatitis, rosacea, lichen sclerosus, anogenital pruritus, and prurigo nodularis.
Most of the topical antihistamines are relatively ineffective at reducing itch. Only topical doxepin, a potent H1 and H2 antagonist, has been shown to significantly reduce pruritus in patients with AD, lichen simplex chronicus, contact dermatitis, and nummular dermatitis. Be careful though of widespread use as it can cause drowsiness, just as the oral use can.
Topical capsaicin can decrease pain and to some extent pruritus although the existence of solid evidence for reducing pruritus is debated.
Topical lidocaine alone or as an eutectic mixture with prilocaine (EMLA) has been used to effectively treat pruritus in patients with notalgia paresthetica, pruritus ani, and postburn pruritus. Potential side effects include allergic contact dermatitis and methemoglobinemia necessitating avoidance in infants and pregnant patients.
Pramoxine is a topical OTC medication that can decrease the itch in patients with xerosis, uremic pruritus, and psoriasis. Its mechanism of action centers around stabilizing membranes of sensory nerves.
Wet dressings are surprisingly effective for almost any itch, anywhere.
Apply a wet cloth wherever the skin itches. Change every 3 hours. Cover with a dry blanket if needed. Use hydrocortisone 1% for face or folds and triamcinolone elsewhere if needed.
Aprepitant is approved for the prevention of chemotherapy-induced emesis and is usually administered for three days only (125 mg, 80 mg, 80 mg). Several studies have shown it to be helpful in recalcitrant pruritus, e.g., idiopathic, brachioradial or Hodgkin's lyphoma related.
Gabapentin and pregabalin are used for neuropathic pain and also have antipruritic effects on many conditions including uremic pruritus. Both gabapentin and pregabalin, which is structurally related to gabapentin, have to be titrated up to an effective dose starting with a low initial dose (Gabapentin initial 100 to 300 mg/d; maximum dosage up to 900 mg/d; pregabalin initial 25 to 75 mg; 300 mg maximum dose).
Very, very rarely, oral cyclosporin may be considered for chronic itch.
Mu-opioid antagonists have an antipruritic effect and may be tried for chronic pruritus.
Various antidepressants have benefit in chronic pruritus. These include amitriptyline, doxepin, mirtazapine, fluoxetine, fluvoxamine and paroxetine. They are particularly helpful in patients with uremic pruritus, cholestatic pruritus or paraneoplastic pruritus [JAAD 2017;77;1068].
Scratching the non-itchy side while staring in the mirror statistically reduced itch [PLoS One. 2013;26;8:e82756]!
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