[cruzin4us (OP)]

Anywhere up to 24 hours before it rains, I break out in an area about the size of a 50 cent piece.  It looks like poison oak and itches like crazy.   I've had this condition for about 20 years.

The odd part is the location on my body changes almost every year.  Right now it is located on the inside of my left knee, but it's been on my elbows, forearms, calf, toe, and even my nipple.  When it was on my nipple, it was during a period of time when I was nursing, so there was excess moisture which may have contributed.

The doctor perscribed a topical medication which always stops the itching, but that's not really my question.

My real [?] is why does this happen?  My friends used to think me nuts, but now have become believers []

Any ideas?

Laurie [8D]

[ROBERT]

Hi Cruzin4us,
people who have arthritis suffer exacerbations in bad weather,

http://www.midwestarthritis.com/html/weather___arthritis.htm

the low atmospheric pressure causes their swollen joints to expand further.
 Rashes can occur simultaneously with arthritis in rheumatic illnesses.
This may explain the association between your rash and rainy weather.

http://www.robsworld.org/barometer.html

[ROBERT]

Hi Laurie,
further thoughts on your "rain-rash".
If your rash coincides with rain, but did not precede it, then it could be due to the clothing you wear when it rains,
e.g. latex allergy to the rubber coating on rainwear (e.g. “mackintosh”),
or allergy to the chemicals on the fabric-conditioner sheet put in the tumble dryer, (e.g. “bounce”) ,
if you only tumble-dry you clothes in wet weather and line dry them at all other times.

The rash on your nipple during nursing could also be latex allergy from you baby’s pacifier,
via your baby’s mouth.

However if your rash really does precede/predict rain then the only triggers I can think of are:-
A drop in atmospheric pressure (my original suggestion above),
increased humidity, or reduction of exposure to sunlight.

Exposure to sunlight can relieve some skin conditions e.g. psoriasis.
If lack of sunlight were the trigger your rash would probably be worse in winter.

http://www.derm.ubc.ca/skincare/psoriasis/psorhand.html