Compositae contact allergy refers to allergic reactions caused by a group of plants commonly known as Compositae. Compositae is an alternative name for the official term Asteraceae. The most important allergens in the Compositae family are sesquiterpene lactones, which are present in the oleoresin fraction of leaf, stem, flower and possibly in the pollen.
Compositae contact allergy presents as dermatitis on areas exposed to flowers or pollens. It mainly occurs in middle-aged and elderly adults during the summer months, but either sex and any age group may be affected at any time of year. In some regions it is called ragweed or parthenium dermatitis. Allergy can be due to direct contact with the plant, with its pollen, or to skin care products that use the plant extracts.
Which plants are responsible for compositae allergy?
The Compositae family refers to plants in which the flower heads are a composite of individual flowers. They are also given the name Asteraceae beacause the flowerheads are star-shaped (aster is Greek for star). These plants include about 20,000 species of flowers, herbs, weeds and vegetables, including asters, daisies and sunflowers. They occur worldwide, and are found in gardens, roadsides and wilderness; they account for 10% of all flowering plants.
Extracts of Compositae are used in topical skin treatments, cosmetics, herbal supplements, natural medicines and foods.
|Common names for some members of the Compositae family|
|Arnica||Artichoke, globe||Artichoke, wild||Bitterweed|
|Chamomile, Roman||Chamomile, German||Champaca of perfumery||Chickweed|
|Costus of perfumery||Cotton thistle||Dandelion||Echinacea|
|Tulip tree||Whitewood of commerce||Wormwood||Yarrow|
How is Compositae allergy diagnosed?
Compositae allergy is diagnosed by patch tests performed on a patient with contact allergic dermatitis. The Standard series of patch test allergens usually contains Sesquiterpene lactone mix (alantolactone, dehydroxosus lactone, costunolide), and may also contain compositae mix.
Related plant allergens include parthenolide, and specific extracts prepared from individual plants such as dandelion, tansy, yarrow, feverfew, chamomile, arnica and chrysanthemum. It may be necessary to test several of these allergens to confirm compositae allergy. In one study, sesquiterpene mix detected 65% and compositae mix detected 87% of compositae-allergic patients, but individual plant extracts were necessary to confirm the diagnosis in all patients. Parthenolide detects 75% of sesquiterpene lactone allergic patients.
Once someone has become allergic to one of the responsible allergens, their immune system is likely to react to similar chemical structures resulting in cross-sensitisation and multiple contact allergies. Thus many patients that are patch test positive to one plant extract also test positive to others.
Other allergens that may be responsible for compositae dermatitis include monoterpenes (e.g., pinene, limonene, terpinene, camphor), coumarin, a sesquiterpene alcohol and a thiophene.
What does Compositae dermatitis look like?
Contact allergy to compositae in gardeners, farmers, forestry workers or florists, may result in serious occupational dermatitis. It may present in several ways.
Dermatitis may affect the backs of the hands only, and/or the palms, or is sometimes confined to the fingertips (sometimes called pulpitis) depending on which sites are in contact with the responsible plant. The dermatitis may be vesicular (blistering), resembling pompholyx, or result in dry red patches.
Airborne contact dermatitis
Airborne contact dermatitis affects the face, neck, hands and arms or all areas exposed to plant pollens borne by the wind. It often results in considerable swelling and blistering as well as redness, dryness, or scaling. The rash may vary according to the season, depending on pollen levels.
In the seborrhoeic pattern of compositae allergy, the dermatitis is most prominent in skin folds such as behind the ears, the sides of the nose, eyelids and neck. It is possible that pollen sticks to moist areas of skin causing more active dermatitis in these sites. The allergen may be transmitted to these sites via the fingertips.
When allergy is severe, the rash may spread to apparently unexposed sites. This may present as erythroderma, a serious condition involving the entire skin surface.
Chronic photosensitivity dermatitis
Patients with chronic actinic dermatitis or actinic reticuloid are frequently found to have contact allergy to compositae on patch testing. They tend to be elderly men with dermatitis affecting the face, neck and hands. It is believed that chronic contact allergic dermatitis to compositae slowly evolves to photocontact dermatitis and then to photosensitivity even in the absence of known contact with compositae. These patients are exquisitely sensitive to ultraviolet radiation so that dermatitis appears on skin exposed to sunlight for just a few minutes.
It is thought that about 20-75% of patients with compositae have some degree of photosensitivity.
Itchy lumps similar to those arising in prurigo nodularis have been the result of contact dermatitis to parthenium in some cases.
If the leaves of the plant are chewed, the lips, tongue and mouth may become inflamed and mouth ulcers may occur.
Allergic systemic contact dermatitis
Generalised dermatitis may occur if the allergen is ingested (e.g., drunk as a tea) and may affect oral mucosa and anus as well as the skin. It may be intensely itchy. The rash appears after several hours reaching a peak two or three days after exposure to the allergen.
A nonspecific itchy red dry rash has also been reported to arise following inhalation of pollen.
Compositae allergy usually persists lifelong, but the dermatitis should clear once the skin is no longer exposed to the plants that are responsible for it. It is therefore very important to find out which plants in your neighbourhood are in the Asteraceae family so contact with them can be avoided. Cosmetics and creams containing Compositae products should not be used. However, most affected individuals may safely eat vegetables of the Compositae family.
Exquisitely sensitive patients may need to dress up fully to protect their skin from airborne pollens when outdoors during the pollen season. Wear long gloves when gardening.
Symptomatic treatment depends on the severity, extent and duration of dermatitis and may include:
- Topical corticosteroids
- Oral antihistamines
- Systemic corticosteroids
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