Medically known as Milaria Rubra, prickly heat erupts when the flow of sweat is blocked. ``Whenever it gets very hot, humid and dusty, our sweat ducts get clogged. Instead of oozing out, the sweat seeps into the skin and causes tiny red boils,'' explains Dr Ranju Rai, Department of Dermatology, PGI.

High temperatures leading to excessive sweating and friction caused by synthetic clothing are the twin reasons for this skin disease.

The areas more prone to it include the back, abdomen, groins and the armpits. Doctors don't mention it, but the nose and forehead also attract these unsightly red blotches. ``Arms and soles are luckier and generally remain free of such eruptions,'' says Dr A S Narula, a dermatologist, ``while folds tend to ttract it.'' Plump persons, beware!

Infants and people less used to the heat are also an easy prey. ``Babies,'' says Dr Rai, ``are more vulnerable because of their immature sweat glands, nursing in humid conditions and blockages in the nappy area.''

Interestingly, it's the obstruction of sweat at a deeper level that leads to the red, hot sensation. As Dr Rai explains: ``When the blockage is at a very superficial level, you get clear, fluid-filled lesions which are symptom-less. These erupt on their own and cause scaling. Prickly heat or sweat-retention syndrome occurs when the blockage is very deep.''

In normal conditions, the red boils subside within three days, but they can recur if the heat persists. ``It is impossible to cure prickly heat if the person continues to work in conditions that cause him to sweat buckets,'' says Dr Narula.

But unlike other ailments, prickly heat doesn't generally worsen. Instead, the skin tends to get acclimatised to the heat and the symptoms become less severe. However, in some cases, especially in infants, it can aggravate and cause pus formation which can be cured only with antibiotics.

However, most of the times all it requires is a bit of cooling. ``Avoid sweating and stay cool if you want to steer clear of prickly heat,'' says Dr Rai. ``Yes,'' agrees Dr Narula. ``We advise patients to stick to an air-conditioned room for a couple of hours. That does the trick.''