Five things...you may not know about
Consultant dermatologist Professor John Hawk looks at diagnosis and treatment of seborrhoeic eczema
1. Seborrhoeic eczema behaves like an allergic dermatitis against a yeast component
Seborrhoeic eczema, or dermatitis, is a very common skin disorder affecting men somewhat more than women. It has onset mostly in young adulthood, but may sometimes
appear in the neonate, usually soon to resolve again; or later life, perhaps associated with the onset of increasingly xerotic skin. It
behaves as if it is an allergic dermatitis against some component of the cutaneous Malassezia ovale yeast, profusely resident on all human skin, and there is now good evidence for this hypothesis.
2. Seborrhoeic eczema seems genetically determined
The condition seems primarily genetically determined, perhaps through the nature of the patient's sebum, although its secretion rate and composition have not been shown to be significantly altered from normal, while concomitant acne seems to occur not infrequently. It is also more common in AIDS and Parkinsonism, the former associated with reduced cell-mediated immunity, the latter with increased sebum secretion.
3. The clinical features are typical but variable, both within and between patients
The clinical manifestations are very characteristic, although they vary considerably between and within patients – but usually always with the same basic features in a given individual. Sunlight may improve but sometimes worsen the condition (at times severely), while humidity and dry, often indoor, conditions may also exacerbate it. Scalp flaking and itching, sometimes with scattered small papules but not usually plaques (commonly known as dandruff) is most typical, although not always present.
Otherwise, any skin may be affected but usually flexures or body folds in a symmetrical pattern.
Thus, the sides of the alae nasi, the nasolabial folds and the upper eyelids are typical sites, while perioral follicular eczema, sometimes with minute monomorphic pustulation, is also possible.
The eyebrows and forehead may also be affected with scaling, while the following are also characteristic: itchy or painful cracking behind the ears; central chest scaling or papules; perianal and natal cleft eczema; and itchy axillary or groin redness or cracking.
The glans penis is also sometimes involved, and widespread, patchy, dry eczema, especially in older subjects, may also occur. In the infant, cradle cap and nappy rash are the usual features.
4. It is best to treat all potentially susceptible sites
Treatment is usually effective, but only if done assiduously. Therefore all potentially susceptible sites are best treated even if not all are of concern to the patient, so as to diminish possible systemically mediated stimulation from other sites.
Usually the daily use of a tar or anti-yeast ketoconazole-containing shampoo controls the whole condition in due course, but initial careful overall emollient use, along with intermittent moderate-strength topical steroid applications (if preferred in combination with an anti-yeast agent such as clotrimazole, miconazole or ketoconazole) is generally needed to settle flares of the
5. Severe eczema may need immunosuppressive therapy
For scaling rash of the face, topical ketoconazole once or twice daily as required is often effective, while oral tetracycline for around three weeks often helps settle any perioral folliculitis. Topical tacrolimus may help some resistant patients, as may courses of oral itraconazole, while for occasional very severe, suberythrodermic disease, oral immunosuppressive therapy may be required.
John Hawk is emeritus professor of photobiology and honorary consultant dermatologist at St John's Institute of Dermatology, St Thomas' Hospital, London
Competing interests None declared