Introduction
Eczema is principally a disorder of infancy and early childhood. Allergic eczema is most often IgE-associated (atopic eczema), but could be non-IgE-associated (non-atopic eczema) as well. Eczema is characterized by extreme pruritus and persistent - often frantic - scratching, which induces papulation, excoriations, bleeding, oozing and crusting, secondary infection, and ultimately thickening or lichenification. Although eczema can occur on any area of the body, there are typical locations of involvement that vary according to age. In infants the area around the lower part of the outer ear is often involved, whereas the typical localization in preschool children is the flexor side of the extremities.
Contact dermatitis
Contact dermatitis is an inflammatory reaction of the skin caused either by irritants or allergens. The immune reaction is cell-mediated, contact chemicals act as haptens, combine with epidermal proteins, and form a complete antigen that induces sensitization. The major causes in children are soaps, detergents (irritants) and chemical ingredients/ allergens of clothing and shoe materials (e.g. nickel and chromate).
Other forms of dermatitis
Other forms of dermatitis such as seborrheic eczema/ dermatitis has certain features which resemble eczema and may coexist with eczema. It usually starts before the age of 2 months and clears spontaneously within 3 or 4 weeks. The essential features are erythema and scaling. The pruritus and papulovesicles characteristic of eczema are absent. In contrast to eczema, the scalp is always involved and successful treatment must include attention to this area. The pathogenesis of seborrheic eczema/ dermatitis is largely unknown.
Urticaria
Urticaria or hives (nettle rash) is a pruritic eruption also affecting the skin caracterized by erythematous, edematous wheals of various sizes which blanche when pressed. An individual wheal lasts from minutes to more than 48 hours. Physiologically, the urticarial eruption mimics the classical wheal and flare reaction.
The prevalence of urticaria is extremely high. Over 20% of the population has had hives at some time. Acute urticaria may occur in any age group and is the type most often seen in children. Chronic urticaria (urticaria that persists for 3 months or more) is more common in young adults than in children and adolescents.
Acute urticaria can usually be controlled symptomatically with antihistamine drugs and elimination of inciting factors (based on history). Often it is self-limited and no underlying cause can be found. The probability of identifying an under-lying cause of chronic urticaria is much less than for acute urticaria i.e. in fewer than half the cases. Allergic IgE-mediated reactions are primarily seen in acute urticaria in children, but the majority of acute urticaria in children is, however, associated with infections.
Prevalence
The prevalence of eczema has been estimated to be 15-20% in childhood, and 33-40% of them were found to be sensitized with allergen-specific IgE antibodies. However, eczema seems to be more prevalent in industrialized areas. The age of onset is during the first year of life in 60% of the patients, however rarely before 2 months of age. Another 30% of the patients manifest eczema between 1 and 5 years of age, and about 10% between 6 and 20 years. As many as one third do not outgrow the disease.
Did you know that:
1 out of 3 infants and young children with eczema has underlying allergy and may benefit from a diet or other form of avoidance - which ones are they? Persistent symptoms should always be tested with an allergy blood test.