Itchy rashes all over. Unknown cause.

This has been affecting me for most of my life.  Periodically, I have a bouts of itchy rashes breaking out all over my body (typically starting initially as clusters on either my torso or limb) which I just don't know the cause of.  I've tried to live with it, but these bouts of have been increasing in frequency in recent years.

If I'm lucky, I might initially feel a sort of "tingle", at that point I look down and see nothing, 5 minutes later there is a microscopic 2mm red patch and begins to rapidly "puff up" and then hardens into a wheal.  It takes about 3-4 days for the itching to go away and for these rashes / wheals to start reducing in size.  THey leaves behind a dark mark which takes months to disappear.  Most of the rashes appear heavily around my torso (particularly around the waist).

These rashes are different to the mosquito bites I sometimes experience.  Any mosquito bites are usually only temporary where the rash puffs up and then disappears within a few hours, leaving no trace.  But these rashes I'm talking about puff up in to a hardened wheal, are extremely itchy, and they hang around.

In the past, I responded by Bathing 2 times a day, daily vacuuming, Weekly Washing of sheets, flea bombing, daily washing and changing of clothes have little to no effect, so I've since given up deviating from my normal cleaning and bathing routine when symptoms first present.  Taking an antihistamine has some moderate effect by reducing the severity of any new rashes (They are smaller and less itchy).

There are no pets in the home. (Neighborhood of standalone single family homes)

In many cases, 1 other family member will present the same rashes in one part of their body a week or so later, but no where near the severity that I experience.  They usuaully have one localized bout on either their arm or upper torso, but that is it.

I do engage in a bit of Outdoor reactional activities, but the last time I did any outdoor activity was a hike 2 weeks ago prior to this latest outbreak.  

I saw my GP and he _believes_ that they were insect bites, did not believe it was scabies.  Other people have suggested allergic reaction to soap and laundry detergent, but we haven't changed the products we used for years.  Similary with the food I've been consuming.

What I don't understand, After about two weeks, without knowingly changing anything, the occurance of rashes will spontaneously stop and no new rashes will occur the next 2-8 months.  There does not appear to be any season cycle or climate which appears to trigger this off.  There just doesn't appear to be any pattern to this madness.

Any possible ideas?

[yarrow]

Gee, it sounds unpleasant and upsetting.  It sounds as though you should definitely see an allergist, and maybe google something called 'chronic urticaria.'