Go to any multi-day walking event in the summer and you will see a red heat rash on the calves of many walkers. The heat rash often starts above the sock line and makes red patches and splotches up the calf. It usually doesn't itch and is believed to be heat-related, since these same walkers don't get it in cooler weather. What is it?
Golfer's VasculitisAsk most physicians about this common rash and they draw a blank. That is probably due to few people seeking medical help for it. The rash usually clears up in a couple of days, usually before they are able to get an doctor's appointment. At last, a paper in the Australasian Journal of Dermatology has described it and proposed naming it "golfer's vasculitis."
Causes of the Heat Leg RashResearchers interviewed several people with the rash and discovered that many underwent extensive allergy testing because they believed they must have been having a reaction to some chemical or plant. But it was simply an irritation of the blood vessels following prolonged exercise in the heat, such as walking for extended periods or playing 18 holes of golf.
The rash is more common in people over 50. Most walkers can't pinpoint anything new they have used that may be causing a reaction. And since so many walkers have it, they couldn't all have contacted the same irritant. The source is simply heat and age--your leg blood vessels getting irritated from the heat.
Prevention and Treatment of Golfer's VasculitisThe research offered no treatment or prevention recommendations. It seems to occur in healthy, active people. The researchers suggest it should not be a health concern and recommend not getting allergy testing, etc.
In my non-medical experience at Breast Cancer 3-Day Walks and walking conventions, this rash appears on a vast range of walkers and commonly goes away by itself after a few days. Pampering yourself after a good long walk by taking a cool bath, sitting with your feet up, or applying cool wet towels to the rash may help relieve discomfort.
Other Heat Rashes
Heat Rash - Prickly HeatUnlike golfer's vasculitis, prickly heat is itchy. It is triggered by blocked sweat glands and causes raised itchy red dots or bumps. It is best treated by getting out of the heat for a few days and not scratching the area.
Heat Rash and Prickly Heat
Itchy Legs SyndromeIf your legs are itchy during or after exercise, with no relation to heat, you may have exercise urticaria.
Itchy Legs Syndrome
Cholinergic UrticariaWith this condition, you break out in tiny itchy hives with an increase in body temperature, whether due to exercise or a hot shower.
Poison Ivy - Poison Oak - Poison Sumac RashPoison ivy rash is seen one to three days after contact with poison ivy, poison oak, or poison sumac in sensitive people. It is very itchy, red, bumpy rash, right at the point of contact, often forming a line where the plant rubbed. It may grow into fluid-filled blisters, and lasts from one to three weeks.
Preventing Poison Ivy and Oak Rash
Source: Robert I Kelly, Jacinta Opie and Rosemary Nixon. "Golfer's vasculitis." Australasian Journal of Dermatology, Volume 46 Page 11 - February 2005