Several readers contacted me after a previous posting about jogging causing itching. The below NIH study may be of interest from people who suffer from this condition and also other urticarias.
A team at NIH led by Dr. Hirsh Komarow is studying physical urticarias caused by water, sun, pressure or vibration (such as caused by exercise or exposure to vibrating tools, etc). Dr. Komarow is recruiting patients for this study and particularly interested in patients with other family members who are affected as well as severe cases. The link to the study is available on the clinical trial.gov site here . If you are interested or are looking for more information, contact: email@example.com or (301) 594-2197.
I’m looking forward to seeing the results of this study.
People often come into the clinic worried about spider bites. While the majority of these concerns turn out not to be spider bites, it does raise the question of what sorts of medical conditions spiders can cause. In the United States, tarantulas (shown on the left) are one type of spider that may be found in the wild and as pets. While tarantulas can bite, a more common form of defense is for the tarantula to throw its hairs at a predator (e.g. at you if it thinks you’re going to attack it!) These hairs have little barbs and are urticating, meaning they can cause urticaria (a fancy word for hives or wheals).
These little barbed hairs can lodge in the skin and cause wheals or, they can also lodge into the eye. When they lodge in the eye, these tarantula hairs cause a condition called ophthalmia nodosa. These barbs in the eye cause the eye to get inflamed and could actually lead to vision loss if severe enough.
Needless to say, if you believe you’ve been attacked by a tarantula, you should probably get checked out. More on other spiders (e.g. black widow, brown recluse, etc.) in future posts.
For some people, scratching the skin leads to raised wheals, demonstrating dermatographism which literally means “skin writing.” Scratching or stroking the skin leads to redness and a wheal of that area. About 5% of the population develops redness and some swelling of scratched areas — this is called simple dermatographism. In symptomatic dermatographism, these areas become itchy as well and the wheals are more prominent. In general, wheals develop about 5-10 minutes after the scratching but sometimes they can develop after a longer period of time. Your doctor can test whether you have dermatographism by gently scratching your skin (
usually your back) and seeing whether a wheal forms.
If you have dermatographism, try to avoid stimuli like scratching which lead to the discomfort. Antihistamines can also offer symptomatic relief.