Itching, or pruritus in dermatology jargon, can be caused by a plethora of skin conditions, not just one. This is a very common symptom and sometimes doesn’t have a rash associated with it. A key player in itch is a molecule called histamine. Mast cells, which permanently occupy the skin, produce and release histamine in response to a host of signals, including allergy, infection, irritation, and nerve impulses. It turns out that the nervous system and the skin are intertwined, such that one system influences the other.
A key player is a specific nerve fiber, called a C-fiber. C-fibers are small, unmyelinated nerve fibers that carry pain, temperature, and itch. In fact, sometimes the body can perceive pain as itch, temperature as pain, or temperature as itch. The recent understanding of the nature of this overlapping mechanism between sensations allows it to be exploited, as dermatologists are able to diagnose and treat itch much more effectively than decades past. For example, applying ice packs (or bags of frozen vegetables) to itchy skin really works because it confuses the nerve messages that interpret temperature as itch.
Dry skin is the number one cause of itch in people. Men’s skin physiology is much different than women’s. A 2013 scientific publication in The International Journal of Cosmetic Science found that whereas skin hydration in women is stable or even increasing over a lifetime, skin hydration in men is progressively decreasing, beginning at the age of 40. So, what can you do about it? First, tone down the temperature of your showers. Hot water used to cleanse the skin, similar to hot water used in washing dishes, can strip the natural fatty protective layer of the skin. This leads to a defective barrier and increases the chances of a reaction to common external allergens, such as mold, dust, and pet hair.
It is also prudent to apply thick moisturizers to the skin after bathing, preferably while the skin is still moist. Vanicream and Eucerin Calming cream (both over-the-counter) are good choices because they restore that natural barrier to the skin by preventing water evaporation. In addition, antihistamines can help, especially for itching at night. Over-the-counter Claritin or Zyrtec are your best bets. Because Zyrtec is considered the most sedating, it is generally recommended to take it only at night. In a recent study, 13.7% of patients experienced drowsiness after a single 10 mg dose.
Caution is advised when taking more than one 10mg dose per day, mainly due to operating a vehicle while drowsy. Antihistamines actually last longer in your skin than your blood, which is why some patients find that a single dose of medication can control symptoms long after it has been excreted from the body. The anti-itch effect will start to kick in about 1 hour after taking the pill and lasts up to 24 hours. Still itchy? See Dana Point Dermatology for a prescription cortisone cream, which is exponentially more powerful than the over-the-counter variety.
Other common causes for itch include infections (like scabies or hepatitis), eczema (red flaky patches on the skin due to inflammation), hives, and kidney or liver problems. More rare causes of itch include dermatitis herpetiformis (a rash that comes with gluten sensitivity), blistering skin disease (like bullous pemphigoid), and medication side effects.
Dana Point Dermatology’s Bottom Line: Itch happens. Consult an expert in the skin if it is driving you mad.
