Contact dermatitis is a delayed skin reaction to direct contact with an irritant or sensitizing agent. It is common among adults in the workplace, especially hairdressers, cleaners, caterers and food-preparation staff, nurses, and mechanics. Be wary of jewelry, hair products, clothing dyes, rubber, leather, glue, cement, raw foods, topical medications, sun creams, make-up, perfumes and plants, as these could be triggers.
Allergic contact dermatitis is a delayed, cell-mediated allergy that develops after exposure to an environmental chemical or metal, for example. However, about 80% of contact dermatitis cases can be linked to chronic exposure to a chemical or cleaning product, which induces a non-allergic localized skin irritation.
Contact urticaria is a sudden-onset, localized outbreak of hives among chefs and food handlers.
Types of Dermatitis
This is a non-allergic skin reaction, often found among people who work in the cleaning industry due to frequent exposure to surfactants in detergents and water. Surfactants such as sodium lauryl sulphate irritate the skin and strip away its natural protective oils. Detergents, cutting oils and solvents used in factories and workshops are frequent triggers. Ammonia residue from urine is a trigger in nappy rashes.
Allergic Contact Dermatitis
Allergic contact dermatitis is common in women and develops after repeated exposure to an allergen. It is a delayed skin reaction to common metals, cosmetics, dyes, and rubber products. The lesions are visible at the site of the allergen contact, are sharply demarcated, and develop over 48 hours. First the area will be red and itchy, followed by the development of crusted vesicles and blisters that, with time, will become thickened skin. Allergies appear at the site of the exposure and will disappear within weeks after the source of the allergy is removed.
The allergens responsible for contact dermatitis are often chemicals that bind to a carrier protein to trigger the delayed immune response. Due to perspiration, the allergen can spread through layers of clothing, for example shoe dye can leach through socks. Arm-pit contact dermatitis is triggered by deodorants that contain formaldehyde and/or fragrances.
Several modern preservatives are causing an increasing number of allergic reactions. Methylisothiazolinone (MI) used as a preservative in wet wipes and emollients; paraben preservatives and perfumes that are added to creams are a growing problem. Paraphenylenediamine (PPD), which is used to darken henna products, is a powerful skin sensitiser and is frequently found in hair products and the cheaper Henna-based skin tattoos. Chlorhexidine surgical cleaning solvents can cause problems for health-care workers.
Contact urticaria is an allergic reaction manifesting as hives appearing within minutes of a protein allergen touching the skin. It is common among chefs (triggered by fresh shrimps, garlic and potatoes), medical staff who wear latex rubber, and animal handlers. Up to 10% of healthcare workers are now allergic to latex and can have reactions ranging from contact dermatitis and allergic rhinitis to asthma or even anaphylaxis.
Photosensitive dermatitis can appear on body parts that are exposed to the sun after contact with potential photo-toxins in foods (such as limes, parsnips and celery); drugs (such as phenothiazines and diuretics); topical sunscreens (para-aminobenzoic acid) and certain perfumes in cologne (musk or oil of Bergamot).
Identifying the trigger
If your trigger is not obvious, before doing tests, our specialists will probably ask questions to narrow down the possible cause. They will want to know when your symptoms get worse and what alleviates them. They will also want to find out about your hobbies and trigger activities, as well your reaction soaps, cosmetics, cleaning agents and lotions. They will probably ask about the exact nature of your occupation and which chemicals are found in your workplace.
Workers most at risk for allergic contact dermatitis include people involved in food preparation, hairdressers, animal handlers, florists, printers, chefs, builders, painters, nurses, motor mechanics, laundry workers, and pharmaceutical factory workers.
Diagnostic Patch Tests
Patch testing is at the heart of diagnosing allergic contact dermatitis. Patches containing drops of the suspected allergens are attached to the skin for 48 hours, at which point the patches are removed and the reactions are checked. After another 48 hours a further check is done as, by this time, irritant reactions will have resolved, but allergic reactions will remain. For each allergen, the reactions are ranked from 0 (no reaction) to 3+ (redness with blistering). False positive results could occur in non-specific hypersensitivity, and false negative results if you are using cortisone creams.
Novomed Allergy & Asthma offer the very comprehensive True Test, which includes extracts of lanolin, nickel, neomycin, Balsam of Peru, chromate, benzocaine, Kathon CG, fragrance mix, colophony, epoxy resin, quinoline mix, thiuram mix, cobalt, formaldehyde, paraben mix, carba mix, black rubber mix, phenylenediamine, ethylenediamine, mercapto mix, thiomersal and quaternium-15.
To control your allergic contact dermatitis, our allergists will take a thorough allergy history, test you for various allergens, and work with you to come up with a strategy to avoid contact as well as appropriate measure to protect the skin, for example using barrier creams.
Avoidance of your allergen is important as a contact allergy is usually permanent. If you are diagnosed with occupational contact dermatitis, you will need to discuss the situation with your employer so that a solution can be reached.
- Topical steroid creams are vital to acute treatment. Where appropriate, an allergist can help you get control of your symptoms with a powerful steroid and then wean you on to a less potent steroid cream.
- Oral steroids might be prescribed for a few days if your condition is resistant to steroid creams
- Antibiotics can treat secondary skin infections
- Oral antihistamines are not usually effective here, but they will reduce itchiness in contact urticaria
- Daily soaking in potassium permanganate and Icthammol 10% in glycerine dressings might be recommended for weepy lesions.
- Avoid all topical skin sensitisers such as antihistamine creams (mepyramine, antazoline, diphenhydramine), tea tree oil, neomycin and benzocaine.