A red spot on the skin is called a “macula” in the terminology of dermatologists, several red spots are called “maculae”. Maculae are not to be palpated above the level of the skin, which means that when palpating the skin with closed eyes, it is not possible to determine where the boundaries of the red spot are. Red patches on the body can appear singly (singular) at a specific location, or several of them scattered over the whole skin or an area, which is then called disseminated (scattered, distributed).
If the individual red spots are connected to each other, flowing into each other, the doctor calls this confluent. A large red spot is also called a flat erythema (reddening of the skin). Red spots on the body can have various causes.
In general, the causes are either infectious, allergic, physical (heat, cold, UV radiation), chemical or caused by the side effects of drugs. Already by carefully inspecting the stains, their size, distribution pattern, limitation and timing, the doctor can gather valuable information about the underlying cause. Medical laypersons often refer to skin changes that are above the skin level and can be felt with closed eyes as red spots. Depending on their appearance, a doctor would then refer to them as papules, pustules or plaques, which makes it very clear how important it is for a doctor to examine the alleged red spots closely.
Diagnosis
Red stains have two main causes. One is a dilatation of the blood vessels that supply the skin and the other is small bleedings from the vessels into the skin. These two causes indicate completely different clinical pictures and can be easily distinguished by the doctor using a glass spatula test.
The doctor presses on the red spot with a transparent glass spatula. If the red spot disappears and the skin turns white, there is a dilatation of the vessels for reasons as yet unknown. If the red spot cannot be pushed away, this is called purpura, i.e. bleeding into the skin due to increased permeability of the vessels. Further indications of the cause of the red spots are provided by their distribution: a distribution over both halves of the body indicates a cause in the organism, a distribution only at a certain point rather an external cause. You can find out more about the risk of infection under Is my skin rash contagious?