Skin Rashes

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).

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What skin conditions often cause itching?

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

• Dry skin
• Eczema
• Contact dermatitis
• Urticaria
• Lichen planus
• Psoriasis
• Folliculitis
• Prickly heat/heat rash

What are the common causes of skin rashes?

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

Red (erythema) but not scaly

• A skin infection called cellulitis.
• An allergic reaction called urticaria.
• Reaction to a medicine you are taking.
• Burns.
• Viral rashes - eg, measles or rubella (German measles).
• Vasculitis. This is a condition involving inflammation of blood vessels, which may occur with various illnesses, including rheumatoid arthritis.
• Erythema nodosum. 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 overactive thyroid gland (hyperthyroidism).
• A red rash may occasionally be due to an inflammatory condition called systemic lupus erythematosus, especially if it is on the cheeks.

Red (erythema) and scaly

• Psoriasis. This is a condition where there is inflammation of the skin.
• Eczema. 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.
• Seborrhoeic dermatitis (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 athlete's foot, groin infection (tinea cruris), ringworm, scalp ringworm or infection with candida.
• Pityriasis rosea. 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 planus. 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 - such as measles or rubella - 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 meningitis or blood infection (septicaemia).

Papules

• Common causes of papules include acne, viral wart, seborrhoeic wart, molluscum contagiosum, scabies, insect bites and skin tags.
• Other causes include psoriasis.

Purpura and petechiae

• These are dark red or purple and don't fade with pressure. 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 cirrhosis.
• Less common causes include vasculitis (eg, Henoch-Schönlein purpura) or a low level of platelets in your blood (eg, thrombotic thrombocytopenic purpura).

Nodules

• Common causes of a nodule include a sebaceous cyst, lipoma, skin cancer, or a wart.
• Other causes include rheumatoid nodules (associated with rheumatoid arthritis) and Heberden's nodes (associated with osteoarthritis).

Blisters

• Skin inflammation, including reactions to medicines, contact dermatitis, eczema. Eczema on your legs may be caused by varicose veins (varicose eczema).
• Diseases of your immune system - eg, bullous pemphigoid.
• Viral infections - eg, chickenpox, hand, foot and mouth disease.
• Skin infection: a germ (bacterial) infection with impetigo or viral infection with herpes simplex (cold sores or genital herpes) or with herpes zoster (shingles).
• Rarer causes include pemphigus and pemphigoid.

Pustules

• Skin infection by a virus (eg, cold sores due to herpes simplex virus) or bacterial germs (impetigo).
• 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 or cancerous (malignant) skin ulcers.