Explainers

How to Describe a Rash – A List of Terms and Corresponding Images


There are various technical terms that are used to describe rashes. Though it is not strictly necessary for a parent or care giver, for example, to know specific technical terms when describing a rash, it helps in understanding diagnoses, treatment and liaising with other medical staff.

The key to sufficiently describing a rash is to observe carefully and closely the affected area.

Technical Terms Used to Describe Rashes

The ‘ordinary’ meanings of some technical terms that are used to describe rashes are given below.

Erythema (or Erythematous)

Image of a Erythema (or Erythematous) Rash
The term ‘erythema‘ simply means ‘red’.

Macule

Image of a Macule Rash
A ‘macule‘ is a small, flat area (or ‘spot’) of discoloured skin (usually less than 5 mm in diameter).

Papule

Image of a Papule Rash
A ‘papule‘ is a small, raised area of skin (less than 5 mm). It usually has a domed top (although it can be flat).

Maculopapular

Image of a Maculopapular Rash
The term ‘maculopapular‘ refers to a combination of small flat ‘spots’ and raised ‘spots’ on the skin. This sort of rash is typical of measles.

Vesicle

Image of a Vesicle Rash
A ‘vesicle‘ is a papule (see above) with a fluid-filled centre. Vesicles are typical of chickenpox rash and ‘cold sores’.

Pustule

Image of a Pustule Rash
A ‘pustule‘ is a vesicle (see below) containing yellow fluid. This fluid usually consists of serum (blood fluid), white blood cells, and the virus that has caused the original infection. The presence of a pustule does NOT mean that the rash has ‘become infected’ with bacteria; pustules are an ‘expected’ event in many viral illnesses.

Nodule

Image of a Nodule Rash
A ‘nodule‘ is a larger swelling on the skin surface (usually more than 5 mm in diameter). It extends deep into skin, and is usually firm to the touch.

Petechiae


Petechiae (pronounced ‘p-TEEK-ee-eye’) are small, red-brown, flat macules (see above) up to 2 mm in diameter. It is important to note that they do not blanch (turn white) when pressure is applied with a finger — in contrast to most rashes in children which DO fade when pressure is applied. Petechiae are caused by tiny spots of blood gathered under the surface of the skin. They are important in diagnosing meningococcal disease and other conditions. Anyone with a non-blanching rash needs to see a doctor promptly.

Purpura

Image of a Purpura Rash
Purpura‘ means areas of little petechiae joined together. These are therefore larger areas (usually more than 2 mm) of bleeding under the skin.

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