What Is Dermatographism?

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Dermatographism is a common, benign skin condition in which even a small amount of pressure—such as scratching—causes the skin to swell along the line to which it was applied. Also known as dermatographic urticaria or "skin writing," the condition is not an allergy, though it can manifest with an allergy-like rash and itching within a matter of minutes.

Dermatographia allergy on skin
atsawin1002 / iStock / Getty Images

Dermatographism Symptoms

The symptoms of dermatographism can vary. In "simple dermatographism," people will simply notice swelling/redness where the skin has been stroked. In "symptomatic dermatographism" (a more rare condition), people will notice significant itching to accompany the redness/swelling where the skin has been stroked. Some people may experience only minor and short-lasting urticaria (hives). Others may develop symptoms that are more profound and aggravating, in some cases lasting anywhere from several hours to several days.

Symptoms of dermatographism include:

  • Raised welts along the line of a mild skin trauma
  • Swelling and redness (erythema)
  • Itching (pruritus)

The dermatographic rash will usually appear within minutes of a scratch or abrasion. If you were to write your name on your skin with a fingernail, it would be readable with raised lettering that is likely sharp and clearly defined.

Dermatographism will usually clear on its own without treatment within 15 to 30 minutes. It rarely leaves any lasting marks on the skin.

Causes

Dermatographism is among the most common forms of urticaria, affecting anywhere from 2% to 5% of the world's population. As common as the condition is, dermatographism remains poorly understood.

There are a variety of theories regarding the cause of chronic forms of urticaria. No theory has been proven. Of the existing theories that are supported, blood from some patients supports each theory and blood from other patients does not support it. Accordingly, there are some medications that work for some people with chronic hives and other medications that work for other people.

These compounds will, in turn, cause tiny blood vessels to swell and tissues to fill with fluid along the line of the trauma.

In addition to scratching, dermatographic urticaria may be caused by tight or abrasives clothes, wristwatches, jewelry, belts, or the ear stems of eyeglasses.

Urticaria can also be caused by environmental and health triggers, some of which may co-exist with dermatographism. Examples include:

Diagnosis

Dermatographism is typically diagnosed by the appearance of the rash under mechanical stress. The doctor may lightly rub the skin with a tongue depressor or pen to see if the characteristic welt develops. Lab tests and imaging studies are generally not required.

If the reactions are especially severe or prolonged, you may be referred to a specializedallergist or dermatologist who can use a tool called a dermographometer to measure your skin sensitivity in response to a preset amount of pressure. This can help direct you to the appropriate treatment.

If the cause is in doubt, the doctor can conduct a differential diagnosis to explore other possible causes for your symptoms, including:

  • Latex allergy
  • Systemic mastocytosis (the abnormal accumulation of mast cells on the skin or internal organs)
  • Urticaria pigmentosa (characterized by brownish welts with itching)

False Dermatographism

There are conditions immunologists refer to as false dermatographism, classified as either white, yellow, or black. They look like dermatographic urticaria but have different underlying mechanisms.

These are other possible diagnoses:

  • White dermatographism: The development of temporarily blanched skin where the skin has been scratched. Capillary vasoconstriction is the implicated mechanism.
  • Yellow dermatographism: Characterized by yellowish welts thought to be caused by deposits of bile acid under the skin (such as can occur with cholestasis)
  • Black dermatographism: A non-allergic phenomenon in which contact with metal causes a blackish welt (likely due to deposits of metallic particles under the outermost layer of skin)

Treatment

Dermatographism is usually not treated unless it is causing severe or prolonged symptoms.

If needed, over-the-counter oral antihistamines, like Allegra (fexofenadine) or Zyrtec (cetirizine), may be recommended to treat acute rash and itching.

Less commonly, a prescription drug called cromolyn sodium may be used to help stabilize mast cells and prevent them from releasing histamine into the skin.

Good daily skin care is needed to prevent the development of dermatographic hives. By keeping the skin soft and well-hydrated with emollient moisturizers, you are less likely to experience dryness that can trigger itching and scratching.

Coping

Because dermatographism rarely requires treatment, efforts should instead be focused on avoiding the things that can trigger a rash. Among important self-care tips:

  • Avoid skin irritants: Harsh soaps, fragranced lotions, alcohol-based cleansers, and perfumes can cause skin irritation, leading to scratching and the onset of rash.
  • Bathe wisely: Hot baths and showers can dry the skin as they strip away much-needed oils. Take shorter baths and showers will cooler water. Pat rather than rub the skin dry. Immediately moisturize to keep the skin soft and hydrated.
  • Wear soft, loose-fitting clothes: Avoid scratchy fabrics, heavy wools, or anything clothes that are tight and abrasive.
  • Keep your fingernails short: Trimming and filing your nails helps reduce the risk of accidental scratches.
  • Drink lots of water: Dehydration can lead to skin dryness and itchiness.
  • Protect yourself from the sun: Excessive sun exposure also causes dryness and itching. When out in the sun, use a minimum SPF 30 sunscreen and moisturize when you return home. Avoid the midday sun, and keep yourself well-covered with a hat, long sleeves, and sunglasses whenever in bright sunlight.

A Word From Verywell

Dermatographism can be aggravating, but it's usually not severe. However, if your symptoms are difficult to control, do not hesitate to see a dermatologist. In some cases, you may find that your symptoms are inflamed by triggers or habits you are entirely unaware of.

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Article Sources
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