Dermatology: Pruritis in the Elderly

What is the most common cause of chronic pruritis in the elderly?

1) Liver or kidney disease
2) Xerosis
3) Seborrheic dermatitis
4) Drug-induced

Answer: Xerosis or dry skin.  However, all the other answers will also cause pruritis in anyone. 

What is the best treatment for chronic pruritis secondary to xerosis?

1) Emollients or barrier creams
2) Topical steroids
3) Topical cannabinoids
4) Topical salicylic acids

Answer: Emollients, especially those with low pH.  If these are applied right after bathing, they will have the most benefit.  Topical steroids reduce pruritis only by reducing inflammation, so can be used when pruritis is secondary to inflammatory skin conditions, such as psoriasis, but may not provide much benefit to dry skin.  Topical cannabinoids may be useful in atopic dermatitis, lichen simplex, prurigo nodularis, and chronic kidney disease-associated itching.  Topical salicylic acid can be used in lichen simplex chronicus.

A low pH is part of the skin's protective function (also called the acid mantel) and primarily helps protect against bacteria and fungal growth. On different parts of the body, the skin's pH varies between 5 and 7. The upper part of the chest and back, where there is greater production of sebum, is where the pH is lowest; while the intertrigious areas (groin; armpit) have the highest pH.  (OTC brands to consider:  Eucerin Daily Replenishing Lotion pH 6-8, KimCare™ Moisturizing Hand & Body Lotion pH 5-7, Aveeno Daily Moisturizing Lotion pH 4.1 - 6.5, Olay Moisturizing Lotion pH 7 - 7.6 )

By reducing the skin pH the damaging effects of both lipases and proteases can be minimised. An emollient for example with a pH of between 4.5 and 5.5 will help to neutralise the effect of the skin-dissolving enzymes.

Cooling agents are generally safe, over-the-counter preparations which contain menthol, camphor, or phenol. These substances stimulate nerve fibers which transmit the sensation of cold to mask the itch sensation.

Topical anesthetics, such as pramoxine and EMLA cream can reduce mild-to-moderate pruritus, and may be combined with coolants.

Topical antihistamines, which block H1-receptors, are effective as antipruritics for urticaria and insect bites. Doxepin is one of the most effective topical antihistamine.

Capsaicin is useful in relieving localized intractable pruritus, by desensitizing nerve endings responsible for itch and pain. It may cause localized burning and stinging initially which limits its use as an antipruritic, but this effect subsides with repeated use. To overcome this, initially use capsaicin four times per day to overcome the irritation, then reduce the number of daily applications. EMLA cream may be used in conjunction with capsaicin to reduce the initial irritation.