Éruptions cutanées

How are skin rashes described?

Skin rashes can be described in the following way:

• Redness of the skin (called erythema).

• Flat abnormally coloured areas of skin (called macules). Macules are often either red, dark red or purple, brown or white.

• Solid raised areas which are up to half a centimetre across (called papules).

• Solid raised areas which are more than half a centimetre across (called nodules).

• Areas of red raised skin (called plaques) and scales, which have a flaky silvery-white appearance.

• Reddish-purple lesions which do not fade with pressure (called purpura):
  

  • If less than one centimetre across then these are called petechiae.

  • If more than one centimetre across then they are called ecchymoses.

• Blisters: these are swellings of the skin containing fluid:

  • If a blister is less than half a centimetre across then it is called a vesicle. If filled with yellow fluid (pus) then it is called a pustule.

  • If a blister is larger than half a centimetre across it is called a bulla (plural is bullae).

What skin conditions cause itching?

Skin disorders that can cause itching include (please click the links to separate leaflets which provide further information):

• Peau sèche.

• Eczema.

• Contact dermatitis.

• Urticaria.

• Lichen planus.

• Psoriasis.

• Folliculite.

• Prickly heat/heat rash.

What causes skin rashes?

Please click the links to separate leaflets which provide further information:

Red (erythema) but not scaly skin rash

• A skin infection called la cellulite.

• An allergic reaction called urticaire.

• Reaction to a medicine you are taking.

• Brûlures.

• Éruptions virales - eg, rougeole ou rubella (German measles).

• Vasculitis. This is a condition involving inflammation of blood vessels, which may occur with various illnesses, including polyarthrite rhumatoïde.

• Erythème noueux. This is a condition which causes red rounded lumps (nodules), most commonly on the shins.

• Redness on the palms of your hands may be caused by liver disease, pregnancy or an .

• A red rash may occasionally be due to an inflammatory condition called lupus érythémateux systémique, especially if it is on the cheeks.

Red (erythema) and scaly skin rash

• Psoriasis. This is a condition where there is inflammation of the skin.

• Eczéma. This is sometimes called dermatitis and also involves inflammation of the skin. It may be caused by an allergy and is then called atopic dermatitis/eczema. This may happen in response to some plants - eg, poison oak or ivy.

• Dermatite séborrhéique (in adults). This is a type of skin rash sometimes called seborrhoeic eczema. In babies it is known as cradle cap.

• Fungal (or 'yeast') skin infection, such as pied d'athlète, groin infection (tinea cruris), ringworm, scalp ringworm or infection with candida.

• Pityriasis rosé. This condition is described as 'self-limiting' and the rash will clear itself naturally.

• Pityriasis versicolor. This is a rash which is caused by a yeast-like germ.

• Lupus erythematosus.

• Lichen plan. This condition mainly affects the skin and causes an itchy rash.

Macules

• Red macules may be due to a reaction to a medicine or a viral rash - tel que rougeole ou la rubéole - as well as other causes.

• A brown macule may be a mole but check with your doctor if a mole changes or you are concerned it might be a melanoma.

• A white macule may be due to a condition which causes pale patches of skin (called vitiligo) or a skin complaint with flaky discoloured areas (called pityriasis versicolor).

• If a macule is dark red or purple and does not fade when you put pressure on it then it is a purpura (see below) and you need to see a doctor urgently. This is because it could be a sign of méningite or blood infection (la septicémie).

Papules

• Common causes of papules include l'acné, viral wart, seborrhoeic wart, molluscum contagiosum, scabies, infectées and skin tags.

• Other causes include psoriasis.

Purpura and petechiae

• These are dark red or purple and don't fade when you press them. You need to see a doctor urgently because there may be a serious cause that needs urgent treatment, such as meningococcal infection.

• However, common causes include injury to the skin or repeated coughing. More serious common causes include liver disease such as cirrhose.

• Less common causes include vasculitis (eg, Purpura de Henoch-Schönlein) or a low level of platelets in your blood (eg, thrombotic thrombocytopenic purpura).

Vascularite

© James Heilman, MD, CC BY-SA 3.0, via Wikimedia Commons

Nodules

• Common causes of a nodule include a sebaceous cyst, lipome, cancer de la peau, or a wart.

• Other causes include rheumatoid nodules (associated with polyarthrite rhumatoïde) and Heberden's nodes (associated with l'arthrose).

Blisters

• Skin inflammation, including reactions to medicines, irritante ou allergique, eczema. Eczema on your legs may be caused by varicose veins (eczéma variqueux).

• Diseases of your immune system - eg, pemphigoïde bulleuse.

• Viral infections - eg, varicelle, maladie de la main, du pied et de la bouche.

• Skin infection: a germ (bacterial) infection with impétigo or viral infection with herpes simplex (boutons de fièvre ou herpès génital) or with herpes zoster (shingles).

• Rarer causes include pemphigus et pemphigoid.

Pustules

• Skin infection by a virus (eg, boutons de fièvre due to herpes simplex virus) or bacterial germs (impétigo).

• Inflammation - eg psoriasis.

• Pustular skin reaction to medicine you are taking.

• Pustules on your face may be acne or rosacea.

Ulcers

Ulcers may be due to venous leg ulcers, pressure ulcers, diabetes skin ulcers ou cancerous (malignant) skin ulcers.

This leaflet is a guide but if you have any concerns, you must telephone or see your GP, especially if:

• The rash doesn't quickly disappear.

• Vous vous sentez mal.

• The rash does not fade with pressure (the best way to test this is to press a glass gently against the rash to see if it fades).

• You are not sure what has caused the rash or have any other concerns.