The erythemas

Complex reactions occurring in the capillaries and arterioles of the skin cause erythema, which is simply redness of the skin. This may present as flat macules or as papules, which are raised above the surrounding skin. The lesions may be transient or last for weeks, constant or variable in distribution, with or without vesicles.

It is possible to recognise specific patterns within this plethora of clinical signs, but even the most experienced dermatologist may be reduced to making a general diagnosis of "toxic" erythema. The best we can do therefore is to recognise the common types of erythema and list the possible causes. It is then a matter of deciding on the most likely underlying condition or group of conditions—for example, bacterial infection or autoimmune systemic disease.

Morphology and distribution

Because there can be the same cause for a variety of erythematous rashes detailed descriptions are of limited use. None the less, there are some characteristic patterns.


The presentation of measles is well known, with the appearance of Koplik's spots on the mucosa, photophobia with conjunctivitis, and red macules behind the ears, spreading to the face, trunk, and limbs. The prodromal symptoms and conjunctivitis are absent in drug eruptions. Other viral conditions, including those caused by echoviruses, rubella, infectious mononucleosis, and erythema infectiosum, may have to be considered.


These rashes are similar to that in scarlet fever, when an acute erythematous eruption occurs in relation to a streptococcal infection. Characteristically erythema is widespread on the trunk. There is intense erythema and engorgement of the pharyngeal lymphoid tissue with an exudate and a "strawberry" tongue. Bacterial infections can produce a similar rash, as can drug rashes, without the systemic symptoms.

Figurate erythemas

These are chronic erythematous rashes forming annular or serpiginous patterns. There may be underlying malignancy or connective tissue disease.

Erythema multiforme

Erythema multiforme is sometimes misdiagnosed because of the variety of lesions and number of possible precipitating causes; some of these are listed in the box on the right.

Erythema from antibiotics

Causes of "toxic" erythema Drugs

• Antibiotics, barbiturates, thiazides Infections

• Any recent infections such as streptococcal throat infection or erysipelas; spirochaetal infections; viral infections

Systemic causes

• Pregnancy; connective tissue disease; malignancy

Erythema multiforme: precipitating causes


Herpes simplex—the commonest cause Mycoplasma infection Infectious mononucleosis Poliomyelitis (vaccine) Many other viral and bacterial infections Any focal sepsis BCG inoculaton Collagen disease

Systemic lupus erythematosus Polyarteritis nodosa Neoplasia

Hodgkin's disease Myeloma Carcinoma

Chronic inflammation


Wegener's granuloma Drugs

Barbiturates Sulphonamides Penicillin

Phenothiazine and many others

Erythema multiforme

Erythema multiforme

Clinical picture

The usual erythematous lesions occur in crops on the limbs and trunk. Each lesion may extend, leaving a cyanotic centre, which produces an "iris" or "target" lesion. Bullae may develop in the lesions and on the mucous membranes. A severe bullous form, with lesions on the mucous membranes, is known as the Stevens-Johnson syndrome. There may be neural and bronchial changes as well. Barbiturates, sulphonamides, and other drugs, are the most common cause.

Histologically there are inflammatory changes, vasodilatation, and degeneration of the epidermis.

A condition that may be confused is Sweet's syndrome, which presents as acute plum coloured raised painful lesions on the limbs—sometimes the face and neck—with fever. It is more common in women. The alternative name, "acute febrile neutrophilic dermatosis", describes the presentation and the pathological findings of a florid neutrophilic infiltrate. There is often a preceding upper respiratory infection. Treatment with steroids produces a rapid response but recurrences are common.

Erythema induratum

Erythema induraturn occurs on the lower legs posteriorly, usually in women, with diffuse, indurated dusky red lesions that may ulcerate. It is more common in patients with poor cutaneous circulation. Epithelioid cell granulomas may form.

This erythema was originally described in association with tuberculous infection elsewhere in the body (Bazin's disease). It represents a vasculitic reaction to the infection, and when there is no tuberculous infection another chronic infection may be responsible.

Annular lesions of erythema multiforme
Lupus Poor Circulation

Annular lesions of erythema multiforme

Annular lesions of erythema multiforme

Blistering lesions of erythema multiforme

Erythema nodosum

Erythema nodosum occurs as firm, gradually developing lesions, predominantly on the extensor aspect of the legs. They are tender and progress over four to eight weeks from an acute erythematous stage to residual lesions resembling bruises.

Single or multiple lesions occur, varying in size from 1 to 5 cm. The lesions are often preceded by an upper respiratory tract infection and may be associated with fever and arthralgia. Infections (streptococcal, tuberculous, viral, and fungal) and sarcoidosis are the commonest underlying conditions. Drugs can precipitate erythema nodosum, the contraceptive pill and the sulphonamides being the commonest cause. Ulcerative colitis, Crohn's disease, and lymphoma may also be associated with the condition.

Erythema induratum
How To Deal With Rosacea and Eczema

How To Deal With Rosacea and Eczema

Rosacea and Eczema are two skin conditions that are fairly commonly found throughout the world. Each of them is characterized by different features, and can be both discomfiting as well as result in undesirable appearance features. In a nutshell, theyre problems that many would want to deal with.

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