Acute contact dermatitis from touching allergenic substances is not common in children as they have much less contact with potential allergens than adults. However, children are more prone than adults to have contact with plant allergens, which may occur while they are playing outside.
Although the rhus tree (Toxicodendrom succedaneum) was once a well-known culprit of plant dermatitis, this has now been declared a noxious weed, and many of these trees have been removed. They are still found in some gardens, however, and have a potent allergen that cross-reacts with the allergens in the ubiquitous plant genus grevillea. Grevillea is currently the most common plant allergen for children.
Grevillea Robyn Gordon, an attractive hardy plant with red flowers, used to be quite ubiquitous but has been removed from public places because of the problem of allergy. Other grevillea varieties such as Superb, Ned Kelly and the silky oak tree are close relatives, and the allergens of these all cross-react with each other.
Allergic contact dermatitis presents with an intensely itchy and often blistering rash. It may cause significant oedema on the face and around the genital area. It often has a streaky, asymmetrical pattern, reflecting where the plant brushed against the skin (Figure 11). Often contact has been very brief and is not remembered by the child.
If untreated, lesions of plant dermatitis tend to keep appearing for several days and may take weeks to resolve. They respond well and rapidly to a short course of oral prednisone, starting with 0.5 mg/kg/day until settled then reducing the dosage over two weeks. An attempt should be made to identify the cause. This can be confirmed by applying a tiny bit of the plant to the skin, which will rapidly reproduce the rash. Take care when doing this as there is a risk of a severe reaction. Do not occlude the plant, and leave it on the skin for only five minutes.
Not all childhood skin conditions are atopic dermatitis, even though this is by far the most common problem. Nappy rash is rarely atopic and is more likely to indicate simple irritation, seborrhoeic dermatitis, C. albicans infection or psoriasis. Several endogenous dermatoses that can present in childhood are often confused with atopic dermatitis, including psoriasis, ichthyosis vulgaris and keratosis pilaris. Psoriasis is the most important of these, and many patients with ‘treatment resistant atopic dermatitis’ presenting to paediatric dermatologists turn out to have psoriasis. Pityriasis alba is a very common and harmless childhood facial depigmenting dermatosis that is most often confused with pityriasis versicolor and vitiligo, both of which are much less common. Acne may occur in babies, most often boys, and is not a cause for concern. The most common allergic rashes in children include florid reactions to insect bites, contact dermatitis from plants and urticarial reactions to viral illnesses. MT