Rashes are very common conditions and can have many causes. Most rashes are not dangerous but rather a mere nuisance. Life-threatening skin rashes are rare, but when they do occur, you must identify them and go to a doctor quickly.
Five potentially life-threatening disorders that have skin rash as the primary symptom are:
All of these diseases have one or more of the following features:
Rash affects the entire body, or most of it. Rash affects both the skin and the mucous membranes. Mucous membranes are the moist linings of the following:
mouth and nose
vagina or urethra, the opening for urine, in women
urethra, opening at the tip of the penis, in men
Rashes have blisters on top of them. Blisters that accompany a serious rash usually have the following features:
Blisters involve the thin outer layer of the skin that covers large parts of the body. This may mean several small blisters about 1 cm across or a few very large blisters several centimeters wide. Blisters are tense (full of fluid) at first, and then may become loose before breaking open. When they do rupture, the skin underneath is moist and usually painful. The underlying skin surface then dries up and crusts over.
Pressing on a tense blister or scratching the skin next to a blister will extend the blister and make it larger. This is a common feature of these skin disorders.
Blisters can involve any or all of the mucous membranes just listed. Blisters in these areas may not be noticeable because they rupture easily, especially in the mouth. Blisters on the mucous membranes that rupture may be very painful. When they occur in the mouth, pain makes it hard to eat or even drink.