By Edward Pullen, MD. Check out drpullen.com, a medical blog for the informed patient.

Pruritus is one of the most common problems seen in the office and is one of the most frustrating for patients because, much of the time, physicians simply treat the symptoms and expect that the pruritus will resolve. Pruritus is the medical term for itching.  Few symptoms are more annoying than pruritus and when patients come into the office with symptoms, they want help.

When we see a patient with pruritus, the first issue is to decide if the pruritus is caused by a primary skin condition or a more serious underlying condition.  When there appears to be a primary skin condition, it can be very difficult to manage.  Making the diagnosis sounds like it should be easy, but can actually be quite difficult because the itching itself often leads to scratching and excoriations that lead to skin inflammation, weeping and sometimes secondary skin infections.

Despite this, most of the time a good history and examination will allow us to tell if there is a primary skin condition causing the pruritus. Common skin conditions causing pruritus include irritant or allergic contact dermatitis (like poison ivy), industrial irritant dermatitis, atopic dermatitis, skin fungal infections, psoriasis, scabies, dry skin (xerosis), lichen simplex and urticaria (hives).  When we diagnose one of these problems, treatment often helps. We can be confident that although the condition may be difficult to clear up, we don’t need to worry about serious underlying medical conditions.

Pruritus without a primary dermatologic etiology is definitely more concerning. When I see pruritus of this type, the duration of symptoms and the history and physical exam are the keys to deciding whether to simply treat the itching with medications or to do further diagnostic evaluation. Pruritus is common enough that if symptoms are only a few days in duration and there are no obvious clues on history suggesting an underlying problem, and nothing on a directed physical exam raises red flags, treatment with a non-sedating antihistamine like cetirazine (Zyrtec) or loratadine (Claritin) is often tried. If a patient has had symptoms for more than 2-3 weeks, a lab evaluation looking for diabetes, liver or kidney problems, thyroid disease and hematologic malignancies is done.

About 14-24% of patients that are referred to dermatologists with pruritus without a skin disorder have a systemic condition causing the pruritus. The list of potential systemic causes is very long but includes hematologic causes, liver and bile duct problems, cancers like lymphomas, endocrine disorders, diabetes, metabolic disorders, neurologic problems, stroke and brain abscesses, tumors and autoimmune disorders.

If a patient has a normal complete blood count, metabolic profile with a fasting blood sugar, TSH to exclude thyroid disease, and no primary dermatologic cause, often I will get a chest x-ray to check for enlarged lymph nodes in the chest as a clue to lymphoma.  If this is negative I will usually treat their itching for a few weeks. If they persist with pruritus, I may refer them to a dermatologist or an allergist for further evaluation. Most of the time, fortunately, no serious causes are found. Still, enough of the time, patients having pruritus lasting for more than a few weeks without an apparent cause is a symptom physicians respect and work diligently to solve.