A look at a common cause of the infamous itch-scratch cycle
Almost anything external can cause an itch: a new fabric softener, environmental allergens, abrasive soaps. In these instances if you avoid the external cause, you shouldn’t itch anymore. But what if the source of the itch is internal? This occurs in a phenomenon called dermatographism where the skin forms exaggerated wheals or hives after being gently stroked. The cause is thought to be due to an excess of histamine being inappropriately released upon physical contact.
I had a patient in his late 60s come in to clinic concerned that he had difficulty sleeping because out of nowhere he would feel a burning and itching sensation throughout his body. He denied starting any new medications, changing detergents or changing anything regarding his daily routine. However, he would scratch and the itching would only intensify. The only relief he got when was he ran his body under cold water.
It sounded miserable. But this is a typical itch-scratch cycle we see in dermatographism. Something in the body causes an itch, so you go to scratch it, more histamine is inappropriately released causing that area to be even itchier, so you scratch some more, more histamine is released, and repeat.
We can test for dermatographism in the office. I’ll take the wooden end of a q-tip and stroke patient’s forearm. One minute later, if it forms a raised lesion, then they likely have dermatographism. I ran this test on our patient, and he indeed formed some impressive welts after a gentle stroke with the q-tip.
Fortunately, we have a laundry list of drugs that can block histamines to treat dermatographism, and they’re categorized into two generations. The first generations include Benadryl, which are very potent anti-histamines but come at the cost of inducing drowsiness. The second generations include Zyrtec (cetirizine) and Allegra (fenofexadine), which can block histamine receptors but don’t penetrate the central nervous system so they in theory shouldn’t cause drowsiness.
Treating dermatographism can be different than treating seasonal allergies. While many people find benefit in just taking one Zyrtec pill a day in preventing season allergies, sometimes we have to quadruple that dose to get control in dermatographism. This was the case in our patient who had previously tried one or two Zyrtec pills without relief. So I started him on 4 pills of Zyrtec a day (spaced throughout the day) and Benadryl at night to help with sleep.
I checked up on him a week later and he endorsed significant improvement in itch to the point where he could get a good nights sleep. I was quite relieved, because if he didn’t get better, the next step would have been a referral to an allergy specialist to identify any possible triggers, and that would mean even more time suffering with itch.