Itchy Skin and Its Many Causes

An old-fashioned solution to coping with back itch. / iStock

By Mary Carpenter

In her update to an earlier post on skin problems in hot weather, Mary discusses notalgia paresthetica (NP) – an intense and sometimes painful itching on the upper back—which occurs more often in summertime and more often to women; is often linked to stress and anxiety; and often goes unreported but suspected to be very common. 

PACKING for a 10-day trip to Africa, D.C. ESL teacher B.A. felt intense itching between her shoulder blades. The diagnosis: notalgia paresthetica (NP), which dermatologists consider “very common” if often undiagnosed and have dubbed “the unreachable itch.” Laguna Beach, California, dermatologist Ally Alai describes NP as “commonly seen in middle-aged white females with a seasonal predilection for warmer summer months”—arising in response to ultraviolet radiation in sunlight.

In contrast, cases of notalgia paresthetica (NP) that are reported and added to official statistics most often occur in patients who have upper back or neck pain related to injury or underlying conditions such as a herniated disc. In these cases, bones or muscles trap and put pressure on nerves—placing NP in the category named by Alai: skin-itch-spine-syndrome (SISS). SISS may have inspired the invention of back-scratchers, fashioned in the past from tree branches, whale bone or a nearby wall for rubbing against.

NP involves both “localized pruritus” or itching; and “dysesthesia”—disruption in the experience of touch-based sensations, according to MyClevelandClinic. Dysesthesia can occur when the brain fills sensory gaps: In the absence of nerve receptors that detect moisture, for example, the human brain combines sensations of temperature and texture to create feelings of wetness.

Similarly, emotions, such as anxiety and depression, can contribute to itching that feels every bit as real as…if there were an obvious cause [like nerve damage],” the site explains. Another example of the emotional component of itching: seeing someone scratch can make another person itch. Besides appearing more common both in middle-aged to older adults and in women, NP symptoms may last longer in those with a higher BMI.

“Pain’s creepy bedfellow” is how Harvard cardiologist Haider Warraich once described itching. The same receptors trigger both sensations; distraction can alleviate both sensations; and both sensations can arise or increase in the presence of mental health issues, including depression and obsessive-compulsive disorder.

Finally, capsaicin, the chili pepper extract that is applied topically, can help treat both pain and itching. More familiar as a general analgesic, capsaicin sends impulses to the brain that produce sensations of warming, tingling, itching, stinging or burning—and then diminishes these responses in a process called “defunctionalization.” In addition, pain relievers like lidocaine as well as corticosteroid creams can help relieve itching.  (Nerve-related NP, on the other hand, may respond better to stronger drugs like gabapentin—or in some cases, to a neck massage.)

Of all causes of itching, the most common is contact dermatitis —which can start with any irritant— a wool sweater, prickly lawn grass. Irritant contact dermatitis is a nonallergic skin reaction to a substance that damages the skin’s outer protective layer and usually develops within minutes to hours after exposure. An allergen—poison ivy, the mango plant, nickel, formaldehyde—can provoke a similar reaction.

Whatever the initial cause of itching, scratching can result in rashes and bumps—which in turn cause more itching, more scratching and more reactions, until the layers of bumpy rash began to look serious. Repeated scratching can also cause the bumps to ooze, creating a good place for bacteria or fungi to grow and produce infection. Independently, fungi can also cause itching, as in athlete’s foot.

In very cold weather, itching can arise in exposed areas of skin. Among other common causes, eczema and psoriasis are both “atopic”—hypersensitivity reactions that occur in a part of the body not in contact with an allergen. Both are traced to a combination of genetic and environmental causes, such as pollen. Psoriasis causes itching that may be similar to that of eczema, often less intense but sometimes accompanied by a stinging or burning sensation that has been compared to that produced by fire ants.

Lichen sclerosis (LS), with symptoms that include itching along with white spots and pain, can be the result of an “overactive immune system.” When linked to previous trauma or infection, LS qualifies as an autoimmune disease in which the body’s immune system causes inflammation and damage in healthy tissue.

For B.A., her physician prescribed capsaicin as well as Zyrtec, an antihistamine often taken for allergic reactions. But what seemed to help most to relieve the itching, she said, was bouncing up and down on rutted roads in the safari vehicle—and maybe getting past the stressful anticipation of her trip. By the time she returned home from Africa, her NP seemed to have disappeared —although  itching continued to recur.

For me, poison ivy has been the main nemesis, although I’ve had contact dermatitis set off by combinations of wooly clothes, dry skin and even absent-minded scratching. Cortisone cream has helped, and the poison ivy has sometimes required a course of prednisone—but the crucial component of treatment is often the most challenging: to stop scratching.


—Mary Carpenter regularly reports on topical subjects in health and medicine.


Leave a Reply

Your email address will not be published. Required fields are marked *