What's Up Doc? I develop mosquito bite-like hives whenever I scratch or rub my skin - MetroWest Daily News
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Q: My skin has always been sensitive, but lately it is worse, and now I develop mosquito bite-like hives wherever I scratch or rub. What could this be?
A: This sounds like a possible case of dermatographia (from the Latin for skin writing), so this will be the topic of today's column. Check with your health care provider to verify that this is the condition you have developed.
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An allergic reaction is an overreaction of the immune system to an allergen (a substance that initiates the reaction) or other stimuli. It is typically mediated by certain cells (for example eosinophils, mast cells, basophils), certain antibodies (typically IgE), certain chemicals (for example histamines) and other factors. Urticaria is a rash of round(ish), swollen-looking, red, often itchy lesions that develop due to an allergy. An example of this is the allergic reaction to poison ivy most of us are familiar with, where most (but not all) people develop urticaria as a reaction to urushiol, the allergen of the oily resin found in poison ivy, poison oak and poison sumac.
Environmental urticaria is where something in the environment, such as heat, cold, mechanical pressure, exercise, vibrations, sunlight or other stimuli from the environment are the stimulus for an allergic reaction. In dermatographia, it is mechanical pressure (things such as scratching, rubbing, and/or other mechanical pressure) that causes the urticaria.
Dermatographia is actually a pretty common condition, affecting 2% to 5% of the population at some point in their lives. It most commonly manifests in the late teens to early adulthood, although it can affect people of any age.
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The symptoms of dermatographia include hive-like welts/wheals (red, swollen, and/or raised lesions) rash which is itchy in only a minority of patients. These lesions develop over the area that had the mechanical pressure applied to it. This rash is localized to the point where the patient can draw or even write on themselves. The lesions of dermatographia typically develop 5 to 15 minutes after the abrasive mechanical stimuli, and usually resolve over 30 to 60 minutes.
The diagnosis of dermatographia is made based on the patient's symptoms, and is verified by recreating the lesions (for example by using a tongue depressor to 'draw' on the patient's skin to reproduce the rash).
The exact cause of dermatographia is not known. It is usually idiopathic (spontaneously occurring with no other associated disorders), although it may be associated with certain conditions (such as hypereosinophilic syndrome), caused by a reaction to a medication (penicillin is the most common medication noted to do this), or related to other maladies.
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Treatments for dermatographia include minimizing the stimuli that cause the symptoms, such as by wearing soft/non-itchy/comfortable clothing, avoiding scratching, keeping your skin moisturized, minimizing bathing in very hot water, and avoiding anything else that causes symptoms. Patients with itching or other bothersome symptoms may take over-the-counter antihistamines as needed. In uncommon cases, other medications, possibly including prescription medications, may be indicated.
Dermatographia is typically a benign condition, although the symptoms can be a nuisance/annoyance to the patient. There is no cure for this condition, but it is typically self-limited and resolves on its own over the course of months to years (although in some people it can last longer). If you have symptoms you think may be from dermatographia you should speak with your healthcare provider to verify the diagnosis and to discuss what treatment, if any, is best for you.
Jeff Hersh, Ph.D., M.D., can be reached at DrHersh@juno.com .
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