What is systemic contact dermatitis?
Systemic contact dermatitis (SCD) or systemically reactivated allergic contact dermatitis (ACD) is dermatitis/eczema that occurs when a person who is already sensitised to a substance through skin contact is exposed to that substance (allergen) via a systemic route. Exposure may be through oral, inhalational, injectable, and trans-mucosal routes.
Systemic contact dermatitis was first described in 1895, where individuals with contact sensitivity to mercury developed dermatitis after systemic mercury exposure. Throughout the years, many other allergens have been identified and the routes of exposure increased significantly.
What causes systemic contact dermatitis?
Systemic contact dermatitis is caused by four main groups of allergens:
- Metals (including nickel, mercury, gold)
- Medications (including aminophylline, corticosteroids, antibiotics)
- Plant and herbal products (including balsam of Peru, propolis, Compositae, perfumes)
- Preservatives and excipients (parabens, formaldehyde, propylene glycol).
The following table shows examples of allergens that have caused contact dermatitis from topical application/exposure and subsequent systemic contact dermatitis after systemic exposure.
|Allergen causing ACD after topical exposure||Allergen causing SCD after systemic exposure|
|Topical cream containing sorbic acid||Foods containing sorbic acid, such as strawberries, candies, margarine and cheese|
|Jewellery, zippers or buckles containing nickel||Food containing nickel such as cocoa, beans, tinned foods. Nickel alloy on an intratubal birth control device|
|Balsam of Peru in cosmetics and perfumes||Spices such as cinnamon, vanilla, cloves that are used to flavour foods, drinks and medicines|
|Formaldehyde in fabrics, cosmetics and paints||Artificial sweetener aspartame used as a sugar substitute in many drinks and foods is metabolized in the body to formaldehyde|
|Parabens in cosmetics and pharmaceutical/self-hygiene products||Paraben-containing foods such as marinated fish products, jams and jellies, pickles and preserves|
|Propylene glycol in topical corticosteroid cream||Propylene glycol in oral antihistamine tablets|
|Direct contact with plants or pollens from the Compositae group of plants||Vegetable and herbs such as lettuce, endive, chamomile and echinacea|
|Ethylenediamine in topical antibiotic/steroid creams||Intravenous or oral administration of aminophylline|
|Neomycin in over-the-counter antiseptic preparations||Intravenous or sub-conjunctival administration of neomycin|
What are the symptoms of systemic contact dermatitis?
Systemic contact dermatitis can present itself in many different ways. The most commonly reported symptom is a flare-up at the site of original dermatitis or prior positive patch test site. In some cases, dermatitis may spread to become widespread. Skin eruptions may occur within hours of systemic allergen exposure.
The most widely studied manifestation of systemic contact dermatitis is pompholyx. This is a common type of eczema affecting the hands (cheiropompholyx), and sometimes the feet (pedopompholyx). It is also known as dyshidrotic eczema or vesicular eczema of the hands and/or feet. This has occurred after oral administration of nickel, cobalt and chromium. It is also triggered after ingestion of balsam of Peru, garlic, and food preservatives and colours.
Another presentation of systemic contact dermatitis is the ‘baboon syndrome’ that causes erythema of the buttocks and upper inner thighs. More recently it has been discovered that many patients with baboon syndrome actually don’t have systemic contact dermatitis but have a reaction to systemic drugs without a history of previous cutaneous sensitisation. Baboon syndrome is now termed symmetrical drug related intertriginous and flexural exanthema (SDRIFE). A much smaller number of patients presenting with baboon syndrome actually do have a true systemic contact dermatitis that is confirmed by a positive patch test to the causative allergen.
In addition to cutaneous lesions, general systemic effects may also occur in patients with systemic contact dermatitis. These include headaches, fever, malaise, nausea, vomiting and diarrhoea.
Who gets systemic contact dermatitis?
Systemic contact dermatitis only occurs in people who have been previously sensitised to a substance through skin contact. Most patients have a diagnosis of allergic contact dermatitis confirmed with patch testing to identify the allergen(s). Patients who cannot comply with allergen avoidance put themselves at risk of recurrent or sustained dermatitis or may progress to systemic contact dermatitis.
Diagnosis of systemic contact dermatitis includes thorough history taking, medical examination and special allergy testing with patch tests. Patch testing is usually necessary to confirm the diagnosis and distinguish it from atopic dermatitis, systemic drug eruption and non-compliance with allergen avoidance. Occasionally oral provocation with the suspected allergen may be performed, however, this should only be done in an inpatient environment as severe reactions may result that may require emergency medical attention.
See individual contact allergens for patch testing recommendations.
What is the treatment for systemic contact dermatitis?
Systemic contact dermatitis should resolve once the allergen is avoided. Medications and natural health remedies should be replaced with alternatives that don’t contain the sensitising agent. Diet restrictions to prevent or minimise the intake of the allergen will also help.
Over-the-counter creams and ointments containing a mild topical steroid, such as hydrocortisone 0.5–2.5%, may be used to help control itching, swelling, and redness. In more severe cases, a prescription topical steroid cream may be required, as well as antibiotics if the skin becomes blistered and infected.
What should I do to avoid systemic contact dermatitis?
If you suffer from systemic contact dermatitis, the best way to prevent any problems is by avoiding all products that contain the allergen you are sensitive to. This can be a painstaking process, as it is often difficult to determine the ingredients in products and foodstuffs.
Your dermatologist may have further specific advice, particularly if you are highly sensitive to particular allergens.