Welt which turns into a cut

Every now and then I get a welt come up on my skin.  Could be on my arm, leg, back, it doesn't matter.  I can go for months without them and then I can have 3 in a week.  Size of the welt varies to 1/4 inch to over 3 inches.  The problem with the welt is once it starts to go down after about 1/2 hour there is a cut in it's place where it was.  It is very sore and tender on the cut.  I have not itched or scratched this area.  While the welt is still there you can see the cut starting to form.  I have asked a dermatologist about it once and he said there was no way this could be happening.  Of course it happens so fast there is no way I could get to a doctor once it starts so he can see what actually does happen.  Any suggestions as to what this is?

[jagesh50]

Whealing usually develops within 5-10 minutes of stroking the skin and persists for 15-30 minutes. A short refractory period after clearance of the wheal has been reported. .I feel what you are experiencing is a part of triple response of lewis,this being known as cholinergic dermographism/.Cholinergic dermographism: A large erythematous line studded with punctate wheals similar to cholinergic urticaria (wheals smaller than classic urticaria

[jagesh50]

Sorry If it is all jargon.After histamine the chemical involved in allergy is released it causes whealing,release of other mediators which open the blood vessels.The first rash is to do with histamine,the second- line is the blood vessels- pain due to leukotrines release.

[Bhupinder Kaur, MD]

Hello,
What you seem to be having is called dermographism. Dermographism is a normal physiological response of the skin. The term literally means writing on the skin. Firm stroking of the skin produces an initial red line (capillary dilatation), followed by an axon-reflex flare with broadening erythema (arteriolar dilatation) and the formation of a linear wheal (transudation of fluid/edema) termed the triple response of Lewis.

The exact mechanism of dermographism remains uncertain. Trauma may release an antigen that interacts with the membrane-bound immunoglobulin E of mast cells, which release inflammatory mediators, particularly histamine, into the tissues. This causes small blood vessels to leak, allowing fluid to accumulate in the skin.

It can be treated by antihistamines or cromoglicate and sometimes steroids, as they prevent the histamine from causing the reaction. As the underlying cause of dermographism is not known, it can last for many years without relief.

I hope it helps.Take care and pls do keep me posted on how you are doing or in case you have any additional doubts.Kind regards.